## 3 Mar 2009

### Hume, A Treatise of Human Nature, Book 1, Part 3, Sect 14 Of the Idea of Necessary Connexion, §§333-368

by [Search Blog Here. Index-tags are found on the bottom of the left column.]

[The following is summary, up to the end where I reproduce this section in full. My commentary is in brackets. Paragraph headings are my own.]

David Hume

A Treatise of Human Nature

Book I: Of the Understanding

Part III: Of Knowledge and Probability

Section XIV: Of the Idea of Necessary Connexion

§333 The Repetition of Necessity

Up until now, Hume has explained the way that we draw causal inferences from present sense experiences. We often find objects or situations to be constantly conjoined. These we come to regard as being necessarily connected.

Now, we know that all our ideas we derive originally from impressions [see §17 for this rule]. So there must be some sort of impression that leads us to have the idea of necessary connection.

Consider we strike a match and it lights. We see that the flame came immediately after we struck the match. And the flame was hovering right above that very match we lit. Also, the match was unvolatile sitting in its box. Had we not scraped the match-head, it would not have blazed.

So when we examine just one pair of causally connected objects we discover only two relations between them:

a) they are contiguous in time and place, and
b) the cause preceded the effect.

We find no other relations between them when we just examine one pair.

Now our candlewick is quite short, so we do not light it on the first strike. In fact, we run through the dozens of matches in the box before finally the last one lights our candle.

Each of the dozens of matches we lit are repetitions of the same causal pairing. So let's see if we may determine any more relations between necessarily connected objects, when we examine more than one instance of their pairing.

We find that for every strike there is a flame. Each strike is like the others. And each flame is like the rest. So like causes produce like effects.

One instance of a certain experience can produce a new idea. However, if we repeat that same experience, we cannot thereby obtain a new idea. For, any idea we obtain will be no different than in the first instance. So the similarity between repetitions does not account for our idea of their necessary connections.

Yet, we cannot say that each repetition is absolutely the same. One time when we strike, we hold the match at one angle. The next time at a very slightly different one. Or even if the angle is the same, sounds in the background are detectably different. So no matter what, some detail will indicate that one instance is somehow different from the rest. Nonetheless, we still associatively group them together. But it is only because one repetition is at least minimally different that it can be considered an addition to the group. Otherwise we would not be able to discern it as a separate but similar experience that might be associatively assimilated with the rest. And it is by means of this assimilation of slightly different ideas that we obtain the additional idea of necessity.

the repetition is not in every particular the same, but produces a new impression, and by that means the idea, which I at present examine. For after a frequent repetition, I find, that upon the appearance of one of the objects, the mind is determin'd by custom to consider its usual attendant, and to consider it in a stronger light upon account of its relation to the first object. 'Tis this impression, then, or determination, which affords me the idea of necessity. (155-156 emphasis mine)

§334 Hume's Simple Solution is Simply Sublime

We should have no problem arriving upon the above ideas, given the material we have already covered. We discussed the basic principles. From those we deduced more principles. It all at first seems quite elementary. This "may seduce us unwarily into the conclusion, and make us imagine it contains nothing extraordinary, nor worthy of our curiosity." (156b) Hume's discovery seems all too simple. But he will not let us forget that he just answered one of philosophy's most cherished questions regarding causality.

But though such an inadvertence may facilitate the reception of this reasoning, it will make it be the more easily forgot; for which reason I think it proper to give warning, that I have just now examined one of the most sublime questions in philosophy, viz. that concerning the power and efficacy of causes; where all the sciences seem so much interested. Such a warning will naturally rouze up the attention of the reader, and make him desire a more full account of my doctrine, as well as of the arguments, on which it is founded. This request is so reasonable, that I cannot refuse complying with it; especially as I am hopeful that these principles, the more they are examined, will acquire the more force and evidence. (156bc)

§335 A More Efficacious Examination of Efficacy

Our questions regarding causation are the most important in philosophy. And in both ancient and modern times, philosophers have debated the quality of causes that makes their effects follow. We may also call this quality 'efficacy.' But Hume thinks that they should first have analyzed our idea for this efficacy, which he will now do.

§336 The Vulgarity of Prior Definitions for Power and Efficacy

Hume will analyze the notion of efficacy first by stating its group of synonyms. The following terms all mean largely the same idea:
a) efficacy,
b) agency,
c) power,
d) force,
e) energy,
f) necessity,
g) connection, and
h) productive quality.

Because these terms all mean about the same thing, we will not advance our understanding of efficacy by using these terms in our definition.

So Hume will reject all the "vulgar definitions, which philosophers have given of power and efficacy." (157a) Instead, he will look to our impressions which brought-about this idea. If efficacy is a compound idea, then it results from compound impressions. But if it is a simple idea, then it arises from simple impressions.

§337 Efficacy is not Efficient

Locke's theory of power is the most general and popular account. Consider that we strike the match. Then a flame results. We see such changes in the world around us. But we do not know how something can come from nothing. There must be some efficient cause that has the potency to produce these new things. So we rationally deduce that there is efficacy or power.

Hume refutes. We must recall two principles that we have already established:
1) We cannot arrive at any original idea by means of reason alone.
2) Consider reason without experience's aid. It can never conclude that a cause is necessary to begin an existence [Hume demonstrates this in §§186-189].

§338 Grasping Efficacy without the Danger of Obscurity or Mistake

So we see that reason cannot by itself produce the idea of efficacy. We must instead derive it from experiences. These instances would exhibit efficacy, which then would impress upon our senses. This impression would in turn impress the idea of efficacy in our minds. We believe that we know the idea of efficacy. So there must be some experience that exhibits it in this way. But perhaps we never find such an experience. This would suggest that in fact we do not have such an idea of efficacy. For, Hume has already refuted the principle of a priori or "innate ideas."

Our present business, then, must be to find some natural production, where the operation and efficacy of a cause can be clearly conceived and comprehended by the mind, without any danger of obscurity or mistake. (158a)

§339 Negating the Obscure and Uncertain Principles of the Pretended Secret Force and Energy of Causes

There have been previous philosophers who "have pretended to explain the secret force and energy of causes." (158b) Hume cites Malbranche as one example.

Hume lists the different ways that bodies have been thought to operate, either by:
a) their substantial form,
b) their accidents or qualities,
c) their matter and form,
d) their form and accidents, or
e) by certain virtues and faculties distinct from the above options.

There are many thousands of variations on such theories. The sheer number of contrary explanations leads us to conclude that none are adequate. Hence we think that we have no reason to believe that matter has efficacy of its own. And we become further convinced of this. For, we note that "these principles of substantial forms, and accidents, and faculties, are not in reality any of the known properties of bodies, but are perfectly unintelligible and inexplicable." (158c)

Philosophers prefer their explanations to be clear and intelligible. But they have resorted to such "obscure and uncertain principles." So they must have been incapable of producing an account based on "the simplest understanding, if not of the senses." Such an explanation is in order. For causation is a phenomenon that we perceive.

Hume concludes that there is no such efficient cause to be found among an object's properties. If he did believe there was such an efficacy, then he would only need to demonstrate it by means of experimentation. But he believes instead a negative conclusion, that this efficacy does not exist. So his only means to prove it is to challenge anyone to show him the experience in which we directly perceive it. If no one can do so, then he has defended his argument as best as he possibly can.

§340 The Inextensive Efficacy of the Cartesians
No philosopher has been able to show this efficacy in object's known qualities. So they conclude that the "the ultimate force and efficacy of nature is perfectly unknown to us and that it is in vain we search for it in all the known qualities of matter." In fact, almost all philosophers hold this opinion. The only way they differ is in the inferences they draw from this conclusion. The Cartesians, for example, first establish the principle that we have access to matter's essence. They then infer that matter's essence is not endowed with any efficacy. So it is impossible for matter alone to communicate motion or to produce any other effects. The essence of matter is extension, which implies mobility. But it does not imply motion. Hence the energy that produces motion cannot be found in extension.

§341 The Power of Descartes' Deity

The above conclusion leads the Cartesians to infer something else. They think that matter is entirely inactive. It is deprived of any power that can produce, continue, or communicate motion. However, our senses detect motion. The power causing it cannot be nowhere. So it must be placed somewhere. They conclude that it must lie in the divine perfect being. This deity is the universe's prime mover. He first created matter. Then endowed it with its first impulse so that it could contain motion. Also, by means of his omnipotence, he supports the existence and motions in the cosmos by continually being the source of efficacy.

§342 Hume's Absurd and Impious Anti-Cartesianism

Hume will refute this theory by reminding us of his basic principles. All ideas are derived from either impressions or some preceding mental perception. So the only way we may have any idea of power or efficacy is if we have some perception of it. The Cartesians note that our bodies are incapable of producing such a perception. They also believe-in a priori or innate ideas, one of which being the idea of a supremely perfect being. So they infer that the deity is the only active being in the universe and also that he is the immediate cause of any alteration in matter.

But Hume refuted the theory of innate ideas. So we cannot know of any such supreme being prior to our experiences. Hence He cannot explain the phenomena of causation that our senses perceive. But the Cartesians might accuse Hume of being impious. So he says we need only recognize that in no experience do we directly perceive this power or efficacy of causation.

if they esteem that opinion absurd and impious, as it really is, I shall tell them how they may avoid it; and that is, by concluding from the very first, that they have no adequate idea of power or efficacy in any object; since neither in body nor spirit, neither in superior nor inferior natures, are they able to discover one single instance of it. (160c)

§343 Matter is Powerless, because We have no Idea of It's Power

The Cartesians argued that matter itself did not have causal powers. Other philosophers argue that in fact matter is endowed with such a real power and energy. But, they also admit that this energy cannot be found in any of matter's known qualities. So they still must explain how we first obtain the idea of their efficacy. Yet, we cannot derive this idea by observing matter. And we have no innate ideas. Hence we "deceive ourselves" if we believe that we have this idea.

All ideas are derived from, and represent impressions. We never have any impression, that contains any power or efficacy. We never therefore have any idea of power. (161b)

§344 Appendix Insertion E
Our Inexplicable Non-Existent Will Power

Some offer a different argument. Consider how it seems we "will" our body to move. So some contend that we feel an energy in our minds that has power or force over our bodies. This gives us the idea of power. Then we transfer that quality onto matter, even though matter by itself does not exhibit this power.

Hume refutes. Consider when we "will" our hands to turn a book's page. We notice two events:
a) our decision to turn the page, and
b) our hand turning the page.
But we do not feel energy shooting from our brains to our hands. So we have no perception of a power connecting the two events. We just see the constant connection between willing an action and performing it. Whatever connects the two is still mysterious to us.

So far from perceiving the connexion betwixt an act of volition, and a motion of the body; 'tis allowed that no effect is more inexplicable from the powers and essence of thought and matter. (632c)
In fact, we also do not experience the "empire" of our wills over our minds. Perhaps sometimes we are somewhat in control of what goes on in our mind. But usually it operates autonomously.

We saw that our only access to necessary causation in matterial objects was our perception of their constant conjunction. Likewise for our mind. The only way we know that our mind or will causes bodily actions is because we find our decisions and our actions to be constantly conjoined.

In short, the actions of the mind are, in this respect, the same with those of matter. We perceive only their constant conjunction; nor can we ever reason beyond it. No internal impression has an apparent energy, more than external objects have. Since, therefore, matter is confess'd by philosophers to operate by an unknown force, we shou'd in vain hope to attain an idea of force by consulting our own minds. (633a)

§345 We Don't Have the Power to Understand Power

Previously Hume demonstrated that we never have abstract ideas. We might have faint ideas. In fact, all ideas are faint impressions of sensations. Hence we may only have ideas which are concrete and specific. We cannot for example think about what a circle is without also having in mind a particular circle with its size and property determinations. So we never think ideas without their specific quantitative and qualitative features. We only have concrete ideas. We never have abstract ones. So our mind never conceives "categories" so to speak. Instead, it has habits of associating together clusters of specific ideas. And it does so according to customary associations of a word to any member in that cluster. So we have often used the term circle when seeing one. Then, when we think the word 'circle,' we have the tendency to call to mind any of those things we saw that we called circles [for more on Hume's argument against abstract ideas, see §§45-61. And in particular, see §61 where Hume gives his impressive white globe example.]

So we cannot have abstract ideas, but rather only specific ones. Hence we cannot have just an idea of power in general. We must instead conceive some specific species or single instance of it. To do so we must have some experience in which our senses perceive causal power without needing also rational deduction to infer its existence. But no one yet can provide us with such an experience. Thus we probably do not have an idea of this causal power; "we deceive ourselves in imagining we can form any such general idea." (162b)

§346 Some Do Not Use the Necessary Words to Explain Causal Necessity

We have no idea for what a causal power might be. So we cannot understand such notions as:
1) a being , divine or otherwise, who has a power or force to bring about effects, or
2) a necessary connection between objects that depends on some efficient causal energy possessed by one of the objects.

In these cases we use common words without them referring to determinate ideas.

Actually, Hume says that perhaps these words do refer to determinate ideas, but they are misapplied when accounting for causation. So Hume will now uncover the source for these misapplied determinate ideas.

§347 No Object Alone Has Causal Force

Consider the lit match.

the effect: fire
the cause: striking the match

Sometimes we light a match by placing it under some other flame. That takes less effort. Also, sometimes we have had to strike the match numerous times before it lit. So we can conceive of the flame without the strike, and the strike without the flame. In fact, if all we consider is the idea for the act of striking or the idea for a flame, we will not find any properties that imply a necessary connection to the other.

'Tis not, therefore, from any one instance, that we arrive at the idea of cause and effect, of a necessary connexion of power, of force, of energy, and of efficacy. Did we never see any but particular conjunctions of objects, entirely different from each other, we should never be able to form any such ideas. (162d)

§348 Repetition's Difference from Its Repetitions is the Source of Causal Power

Now imagine instead that we have many candles to light. So we must light every one in the box to finish the job. And suppose we are young. This is our first experience with matches. The first one we successfully strike will create a new idea of the conjunction between striking and fire. Then on our second strike, we might anticipate the fire, but still be a bit surprised. By the end of the box, we strike the match without even looking. We don't need to see the flame anymore to infer that it will be there.

suppose we observe several instances, in which the same objects are always conjoined together, we immediately conceive a connexion betwixt them, and begin to draw an inference from one to another. This multiplicity of resembling instances, therefore, constitutes the very essence of power or connexion, and is the source from which the idea of it arises. (163a emphasis mine)
We want to understand causal power.
And we know that all ideas are copies of sense-impressions. Different sense impressions produce different ideas, and same sense impressions produce same ideas.
Now consider the second time the young candle-lighter lit a match. The first time produced the idea of the conjunction of match-striking and fire. The second produced another such idea. So there was no new idea. But he repeats the process many times. After a number of repetitions, he comes upon the idea of causal power or necessity.
So the repetition itself must have had its own effect on us, which gave us the impression of causal necessity. So Hume will try to see how we obtain the notion of causal power from repetition.

Did the repetition neither discover nor produce anything new, our ideas might be multiply'd by it, but wou'd not be enlarg'd above what they are upon the observation of one single instance. Every enlargement, therefore, (such as the idea of power or connexion) which arises from the multiplicity of similar instances, is copy'd from some effects of the multiplicity, and will be perfectly understood by understanding these effects. Wherever we find anything new to be discover'd or produc'd by the repetition, there we must place the power, and must never look for it in any other object. (163c.d emphasis mine)

§349 Our Reason Lacks the Power to Reason about Power

We often experience the repetition of similar objects conjoined by succession and contiguity. But because they are the same conjunctions, they produce the same idea. Hence each repeated instance "discovers nothing new in any one of them." So consider the second time the candle-lighter struck the match. He inferred it would light. But that is not a new idea.

And consider if we tried to rationally draw an inference from these repeated cases. We discussed already the other philosophers who "deduced" that there must be some power or efficacy that explain's causal necessity. So they want to rationally conclude that the repeated instances have this power. But first they must explain how we obtained this idea of "causal power" to begin-with. For not any one experience provides it.

wherever we reason, we must antecedently be possest of clear ideas, which may be the objects of our reasoning. The conception always precedes the understanding; and where the one is obscure, the other is uncertain; where the one fails, the other must fail also. (164a)

§350 Repetition Changes Nothing in the Repeated Objects

To illustrate his next point, Hume has us imagine that twelve months ago we saw one billiard ball impact another and communicate its motion. And consider that we today saw billiard balls collide again this way. The communicated impulse in both cases is entirely different and unrelated. However, we consider each to be repetitions of the same sort of causal relation.

These impulses have no influence on each other. They are entirely divided by time and place; and the one might have existed and communicated motion, tho' the other never had been in being. (164bc)
So the repetition changes nothing in the objects that repeat [this will prove an important point in Deleuze's commentary.]

'Tis certain that this repetition of similar objects in similar situations produces nothing new either in these objects, or in any external body. (164b)

§351 Hume's Argument is Perfectly Unanswerable

So we know that repetition does not uncover or produce anything new in the constantly conjoined objects. Nonetheless, it is only by means of the resemblance between repeated cases that we obtain the ideas of necessity, power, and efficacy. So these ideas do not represent qualities that the objects possess.

Similar instances are still the first source of our idea of power or necessity; at the same time that they have no influence by their similarity either on each other, or on any external object. (164d)
This argument does not lead us to our answer; for, it is "perfectly unanswerable." But we want to learn the origin of our ideas for causal power and necessity. So to do so, we must turn to some other line of inquiry.

§352 Repetition Impresses Our Mind With the Notion of Necessity

So we experience several instances of constantly-conjoined objects. None of the instances has any influence on the others. Nor do any produce new qualities in the others which might provide the "model" for the idea of causal necessity. But somehow the resemblances between repetitions do give us such an idea. For, after many cases, our minds move from cause to effect automatically, as though they were necessarily connected.

after we have observ'd the resemblance in a sufficient number of instances, we immediately feel a determination of the mind to pass from one object to its usual attendant, and to conceive it in a stronger light upon account of that relation. This determination is the only effect of the resemblance; and therefore must be the same with power or efficacy, whose idea is deriv'd from the resemblance. (165a.b)
Because these resembling instances repeat so much, we are led to conceive the notion of a causal power or necessity governing their conjunction. Each instance is utterly different from the others. Only the mind unites them [this point will prove important for Deleuze's discussion of our body as a "momentary mind," because it does not retain impressions like the mind does.]

The several instances of resembling conjunctions lead us into the notion of power and necessity. These instances are in themselves totally distinct from each other, and have no union but in the mind, which observes them, and collects their ideas. (165bc)

So we experience continual repetition of resembling conjunctions. After a while, our mind performs an automatic motion. It moves from the sensation of the cause to the conception of the effect, even if the effect is not present to the senses. This very movement itself produces an "internal impression" in our mind. This impression is the idea of causal necessity.

Necessity, then, is the effect of this observation, and is nothing but an internal impression of the mind, or a determination to carry our thoughts from one object to another. (165c)

§353 Necessity is a Habit that We Happen to Maintain

So we think there is a necessary connection between causes and effects. This necessity is the foundation for our making inferential moves from one to the other.

And, the foundation for our causal inferences is the transitional move our mind makes on account of the accustomed union between the objects.

So we see that two things are the same:
1) the necessity of causal conjunction, and
2) our habitualized inferences from causes to effects.

§354 Necessity is an Internal Impression

We know that all ideas arise from impressions. But there is no impression from external objects that can give rise the idea of necessity. Hence we must obtain this idea from an internal impression, or, an impression of a reflection [see §24 for a discussion on impressions of reflection.]
There is only one such internal impression that could possible produce the idea of necessity: the impression that is made by our mind's customarily moving from an object to its usually-attendant idea.

The idea of necessity arises from some impression. There is no impression convey'd by our senses, which can give rise to that idea. It must, therefore, be deriv'd from some internal impression, or impression of reflection. There is no internal impression, which has any relation to the present business, but that propensity, which custom produces, to pass from an object to the idea of its usual attendant. This therefore is the essence of necessity. (165d)

Objects do not possess necessity. It is only something to be found in our minds.

necessity is something, that exists in the mind, not in objects; nor is it possible for us ever to form the most distant idea of it, considered as a quality in bodies. (165-166)

§355 Necessity is a Force of the Imagination

We know it is necessary that 2 x 2 = 4, and that all the angles of a triangle add-up-to two right angles. But how did we obtain knowledge of these necessities? We needed to compare triangles to right angles. And we needed to compare 2's to 4's. We found that in all instances of triangles there was a total value of their angles that equaled two right angles. And we found that in all causes of doubled 2's, the total value was four. In this way our minds come automatically to move from the idea of triangle to the idea of two right angles, and from the idea of doubled 2's to the idea of four.

Likewise when we deem a causal relation to be necessary. It also comes from a repetition of our mind's moving from one mental perception to another one.

Some have erroneously concluded that causal objects have the power to necessarily bring-about their effects. But really this power is the force of our habitual inferences to evoke and vivify a habitually-associated idea.

The efficacy or energy of causes is neither plac'd in the causes themselves, nor in the deity, nor in the concurrence of these two principles; but belongs entirely to the soul, which considers the union of two or more objects in all past instances. 'Tis here that the real power of causes is plac'd along with their connexion and necessity. (166a)

Necessity is Grounded in Our Experiences and Not in Our Reasoning

We cannot really say that either the repetition or the idea of necessity came first. They both develop by means of each other. And both are the source of one another. Hume says this is the most difficult paradoxical truth he espouses. But he holds this opinion because our investigations prove it to be true. We must keep in mind that no one object of a conjoined pair logically implies the other. The repetition of their constant conjunction does not change anything in the object. It only influences our mind to infer the idea of causal power or necessity.

any two objects or actions, however related, can never give us any idea, of power, or of a connexion betwixt them: that this idea arises from the repetition of their union: that the repetition neither discovers nor causes any thing in the objects, but has an influence only on the mind, by that customary transition it produces: that this customary transition is, therefore, the same with the power and necessity; which are consequently qualities of perceptions, not of objects, and are internally felt by the soul, and not perceiv'd externally in bodies. (166c.d)

We might be astonished by this above extraordinary finding; "and this astonishment changes immediately into the highest degree of esteem or contempt, according as we approve or disapprove of the subject." (166d) Hume has laid out his hypothesis simply and clearly. But he still fears his reader will reject it on account of some bias they hold.

§357 We might Reject Hume's Thesis If We are Biased Towards Objects

To understand this bias against Hume's perspective, we first might imagine traffic lights at intersections. Perhaps this light is hard to see if you are the first one in line. But the first in line is the first one who must go when the light turns green. As is common at this intersection, the light turns green, and the first driver is not aware. Then all the cars behind the first car honk their horns to notify that first driver he needs to move. And suppose we work at a food stand on that corner, so hundreds of times a day we witness the conjunction of horns and traffic lights turning green. Then, when driving home, we stop at some other intersection where the light is perfectly visible to everyone. So no-one honks. Nonetheless, when it turns green, you immediately feel anxious as though someone were honking at you. So we see that

as certain sounds and smells are always found to attend certain visible objects, we naturally imagine a conjunction, even in place, betwixt the objects and qualities, though the qualities be of such a nature as to admit of no such conjunction, and really exist no where. (167b)
Now consider every time we notice a causal relation between objects. In each instance, there are objects involved in the relation. So we might come to think that their causation has something to do with their objectivity. This is the source of the bias against Hume's theory. But instead we could notice that in each case of causally-conjoined objects, there is also a subjective internal mental motion that moves from the perception of the cause to the idea of the effect. So it is equally explicable that causation is a creation of the human mind.

§358 Some Might Think Hume has It Backwards

On account of the above biases, many will reject this theory as absurd. For surely the efficacy of causation lies in the object and not in our minds, they might think. Causes seem to operate without our mental participation. To take Hume's position, some will say, is to "reverse the order of nature, and make that secondary, which is really primary." (167d)

§359 But Let's Not Expect the World to Operate Like the Human Mind

Hume refutes this objection. He begins by taking up their position that causal power exists in the objects themselves. But we saw that there is no quality in any object that implies such a power. Yet, we may only obtain our ideas from impressions. Thus, if we suppose that causal power is a property of certain objects, we will never be able to obtain a clear idea of what such a causal power is. For, we cannot perceive it. So, if we were to claim that objects have this power whether we recognize it or not, we are making a statement whose key term has no meaning for us.

If we have really no idea of a power or efficacy in any object, or of any real connexion betwixt causes and effects, it will be to little purpose to prove, that an efficacy is necessary in all operations. We do not understand our own meaning in talking so, but ignorantly confound ideas, which are entirely distinct from each other. (168b)

Thus Hume thinks it to be more sensible to conclude that causal power is really an associative force of our minds. This force moves our mind's attention from one object to its usual partner. Such a forced movement would surely also leave some impression on our minds. It is this impression that constitutes our idea of causal necessity.

But many of us project this internal associative force upon the objects around us. As a result, "obscurity and error begin then to take place, and we are led astray by a false philosophy." (168c)

§360 OK, We Will Admit that Reality is Independent to Us,
But Let's Not Get Carried Away and Say Objects Have Causal Powers

Hume is willing to admit these possibilities, that
a) the operations of nature are independent of our thought and reasoning, that
b) objects actually do bear to each other the relations of contiguity and succession, that
c) like objects may be observed in several instances to have like relations, and most importantly, that
d) all this is independent of, and antecedent to the operations of the understanding.
However, we cannot observe any power or necessary connection in the objects themselves. So we go to far if we ascribe such a power to them.

this is what we can never observe in them, but must draw the idea of it from what we feel internally in contemplating them. (169a)

§361 We Should See Things from Our Own Point of View, and Not from the Object's Viewpoint

Objects confront us. They immediately then convey to our minds a lively idea of another object that is usually apprehended along with them. These pre-determined associations of the mind form the objects' necessary connections.

But now let's switch our point of view from the objects to our perceptions of them. Before from the objective point of view, the object caused our mental association. But from the perspective of our perceptions, the sense-impression now causes our inference to the idea, which is the impression's effect. Now their necessary connection is the force of the motion our mind makes when moving from impression to evoked idea.

So we cannot know the causal powers that objects might actually have in themselves. And also, we cannot know the reason why our minds work the way they do. But we can study our experiences of causal relations, and say whatever is apparent to us.

The uniting principle among our internal perceptions is as unintelligible as that among external objects, and is not known to us any other way than by experience. (169c)

§362 Why We are Moving Backwards to Explain Cause and Effect

Notice that we began our discussion of causal relations by first examining the way we make causal inferences. Then afterwards we explained what that causal relation was that allowed for these inference. This might seem backwards. But we also saw that causal relations and causal inferences are bound-up tightly with each other.

as the nature of the relation depends so much on that of the inference, we have been obliged to advance in this seemingly preposterous manner, and make use of terms before we were able exactly to define them, or fix their meaning. (169d)

So we chose this path to establish more basic principles. With these we will now give a formal definition for cause and effect.

§363 Our Definitions for Causation May Not Satisfy Those Who Want to Reason Beyond What Experience Tells Us

Hume says that there are two possible definitions for the causal relation.

Definition 1
A cause is an object. It precedes a contiguous object. All objects resembling the cause are likewise considered to precede contiguous objects that resemble the effect.

This definition might be criticized for defining a cause by something external to it. So we might consider the alternative.

Definition 2
A cause is an object. It precedes a contiguous object. The cause is united with its effect. So when our mind conceives the idea of the one, it thereby conceives the other. And, when we have a sense impression of the cause, we obtain a more lively idea of the effect.
But someone might still say that we are defining cause by something external to it, namely, by the effect that accompanies it.

Hume says that he can give no better definition. If one is desired, we have to produce it ourselves.

I know no other remedy, than that the persons, who express this delicacy, should substitute a juster definition in its place. But for my part I must own my incapacity for such an undertaking. (170bc)
Hume can give no other definition. For he is only able to see causes and effects in this way. The causal relation is not so much a thing as it is a force or tendency in the mind's associative habits. So when we define cause, we are really just defining one pole in that forced motion.

§364 We have no Cause to Distinguish Causes

Hume will draw some corollaries from his conclusions. And he will address some errors that philosophy has made in these matters.

1) We see that from Hume's theory there is no way to distinguish types of causes. They are all of the same kind. But in philosophy we often distinguish efficient causes from formal, material, expemplary, and final causes. For Hume, causal efficiency is obtained whenever there is a constant conjunction of objects. So in that sense, every cause is efficient in Hume's system.

Also, philosophers might say that the occasion that gives rise to something else is different from a cause. But according to Hume's theory, there could be no such distinction.

If constant conjunction be implyed in what we call occasion, it is a real cause. If not, it is no relation at all, and cannot give rise to any argument or reasoning. (171b)

§365 There is No Necessity in Denying Necessity

2) We advance the above reasoning. There is only one kind of necessity. For there is only one kind of cause.

Consider that it is necessary for impacting bodies to communicate their motions. We call this a physical necessity. But also consider that it is necessary we tell the truth when we give testimony as a crime witness. Some philosophers might call this a "moral necessity." But Hume says there is no grounds for such a distinction. If something is necessary it is because it is constantly conjoined to something else.

So when things are causally conjoined, there is a "physical necessity" to their causal relation. If there is no such constant conjunction, there is also no physical necessity that they be linked. This is chance.

But just because there are different degrees of constancy does not mean there is no true necessity. So long as the mind habitually moves from one idea to another, there is necessity.

§366 We Cannot Distinguish Power from Its Exercise

[Consider that a spring normally has little 'causal power.' But when you compress the spring, it then has the causal power to push something. But first we need to place something against it that it has the power to push on its own, for example a piece of paper. Then we lay the paper on the compressed spring and release it. The paper shoots away. So it is as though the spring had causal power that was in a potential form. And the exercise of that causal power is different from its stored potency. But in Hume's system, we might say that compressed springs are constantly conjoined with outward movement when circumstances allow for it. But that does not mean there was some potential causal power that was different from its actually using that power.]

The distinction, which we often make betwixt POWER and the EXERCISE of it, is equally without foundation (171d).

§367 A Beginning Has a Cause, but It is Not Caused

3) We might also define a cause as an object that precedes a contiguous object. All other objects resembling the cause have its position of priority to like effects. So the beginning of any effect will always be attended by its cause.

Or, we might define a cause as an object preceding a contiguous object. The two are united in the imagination. So when we conceive the cause, our imaginations form the idea of the effect. And if we have a sense-impression of the cause, that will enliven the idea of the effect. [Likewise for this definition, the beginning of an effect will be attended by its cause.]

§368 We Only Causally Infer Ideas We Have Experienced Before

We see the dawn's glimmer. Then we infer sunrise is arriving. So we reasoned that the sunrise exists by means of its cause. In fact, we always infer existence through such causal relations.

A sensation leaves an impression in the mind. This is an idea. And it is the only way we obtain ideas.

So if we infer some idea from another one, that means we experienced both of them before. And if we experienced them before, we can conceive them.

But if we cannot conceive the idea, then no other idea will evoke it. So we cannot rationally deduce the existence of some object we never experienced before.

However, we need not have a full knowledge of the object to know it exists. For, we can at least know some of its qualities to exist.

From the original text:

#### Sect. xiv. Of the Idea of Necessary Connexion.

Having thus explained the manner, in which we reason beyond our immediate impressions, and conclude that such particular causes must have such particular effects; we must now return upon our footsteps to examine that question, which [Sect. 2.] first occured to us, and which we dropt in our way, viz. What is our idea of necessity, when we say that two objects are necessarily connected together. Upon this head I repeat what I have often had occasion to observe, that as we have no idea, that is not derived from an impression, we must find some impression, that gives rise to this idea of necessity, if we assert we have really such an idea. In order to this I consider, in what objects necessity is commonly supposed to lie; and finding that it is always ascribed to causes and effects, I turn my eye to two objects supposed to be placed in that relation; and examine them in all the situations, of which they are susceptible. I immediately perceive, that they are contiguous in time and place, and that the object we call cause precedes the other we call effect. In no one instance can I go any farther, nor is it possible for me to discover any third relation betwixt these objects. I therefore enlarge my view to comprehend several instances; where I find like objects always existing in like relations of contiguity and succession. At first sight this seems to serve but little to my purpose. The reflection on several instances only repeats the same objects; and therefore can never give rise to a new idea. But upon farther enquiry I find, that the repetition is not in every particular the same, but produces a new impression, and by that means the idea, which I at present examine. For after a frequent repetition, I find, that upon the appearance of one of the objects, the mind is determined by custom to consider its usual attendant, and to consider it in a stronger light upon account of its relation to the first object. It is this impression, then, or determination, which affords me the idea of necessity.

I doubt not but these consequences will at first sight be received without difficulty, as being evident deductions from principles, which we have already established, and which we have often employed in our reasonings. This evidence both in the first principles, and in the deductions, may seduce us unwarily into the conclusion, and make us imagine it contains nothing extraordinary, nor worthy of our curiosity. But though such an inadvertence may facilitate the reception of this reasoning, it will make it be the more easily forgot; for which reason I think it proper to give warning, that I have just now examined one of the most sublime questions in philosophy, viz. that concerning the power and efficacy of causes; where all the sciences seem so much interested. Such a warning will naturally rouze up the attention of the reader, and make him desire a more full account of my doctrine, as well as of the arguments, on which it is founded. This request is so reasonable, that I cannot refuse complying with it; especially as I am hopeful that these principles, the more they are examined, will acquire the more force and evidence.

There is no question, which on account of its importance, as well as difficulty, has caused more disputes both among antient and modern philosophers, than this concerning the efficacy of causes, or that quality which makes them be followed by their effects. But before they entered upon these disputes, methinks it would not have been improper to have examined what idea we have of that efficacy, which is the subject of the controversy. This is what I find principally wanting in their reasonings, and what I shall here endeavour to supply.

I begin with observing that the terms of EFFICACY, AGENCY, POWER, FORCE, ENERGY, NECESSITY, CONNEXION, and PRODUCTIVE QUALITY, are all nearly synonymous; and therefore it is an absurdity to employ any of them in defining the rest. By this observation we reject at once all the vulgar definitions, which philosophers have given of power and efficacy; and instead of searching for the idea in these definitions, must look for it in the impressions, from which it is originally derived. If it be a compound idea, it must arise from compound impressions. If simple, from simple impressions.

I believe the most general and most popular explication of this matter, is to say [See Mr. Locke, chapter of power.], that finding from experience, that there are several new productions in matter, such as the motions and variations of body, and concluding that there must somewhere be a power capable of producing them, we arrive at last by this reasoning at the idea of power and efficacy. But to be convinced that this explication is more popular than philosophical, we need but reflect on two very obvious principles. First, That reason alone can never give rise to any original idea, and secondly, that reason, as distinguished from experience, can never make us conclude, that a cause or productive quality is absolutely requisite to every beginning of existence. Both these considerations have been sufficiently explained: and therefore shall not at present be any farther insisted on.

I shall only infer from them, that since reason can never give rise to the idea of efficacy, that idea must be derived from experience, and from some particular instances of this efficacy, which make their passage into the mind by the common channels of sensation or reflection. Ideas always represent their objects or impressions; and vice versa, there are some objects necessary to give rise to every idea. If we pretend, therefore, to have any just idea of this efficacy, we must produce some instance, wherein the efficacy is plainly discoverable to the mind, and its operations obvious to our consciousness or sensation. By the refusal of this, we acknowledge, that the idea is impossible and imaginary, since the principle of innate ideas, which alone can save us from this dilemma, has been already refuted, and is now almost universally rejected in the learned world. Our present business, then, must be to find some natural production, where the operation and efficacy of a cause can be clearly conceived and comprehended by the mind, without any danger of obscurity or mistake.

In this research we meet with very little encouragement from that prodigious diversity, which is found in the opinions of those philosophers, who have pretended to explain the secret force and energy of causes. [See Father Malbranche, Book vi. Part 2, chap. 3. And the illustrations upon it.] There are some, who maintain, that bodies operate by their substantial form; others, by their accidents or qualities; several, by their matter and form; some, by their form and accidents; others, by certain virtues and faculties distinct from all this. All these sentiments again are mixed and varyed in a thousand different ways; and form a strong presumption, that none of them have any solidity or evidence, and that the supposition of an efficacy in any of the known qualities of matter is entirely without foundation. This presumption must encrease upon us, when we consider, that these principles of substantial forms, and accidents, and faculties, are not in reality any of the known properties of bodies, but are perfectly unintelligible and inexplicable. For it is evident philosophers would never have had recourse to such obscure and uncertain principles, had they met with any satisfaction in such as are clear and intelligible; especially in such an affair as this, which must be an object of the simplest understanding, if not of the senses. Upon the whole, we may conclude, that it is impossible in any one instance to shew the principle, in which the force and agency of a cause is placed; and that the most refined and most vulgar understandings are equally at a loss in this particular. If any one think proper to refute this assertion, he need not put himself to the trouble of inventing any long reasonings: but may at once shew us an instance of a cause, where we discover the power or operating principle. This defiance we are obliged frequently to make use of, as being almost the only means of proving a negative in philosophy.

The small success, which has been met with in all the attempts to fix this power, has at last obliged philosophers to conclude, that the ultimate force and efficacy of nature is perfectly unknown to us, and that it is in vain we search for it in all the known qualities of matter. In this opinion they are almost unanimous; and it is only in the inference they draw from it, that they discover any difference in their sentiments. For some of them, as the CARTESIANS in particular, having established it as a principle, that we are perfectly acquainted with the essence of matter, have very naturally inferred, that it is endowed with no efficacy, and that it is impossible for it of itself to communicate motion, or produce any of those effects, which we ascribe to it. As the essence of matter consists in extension, and as extension implies not actual motion, but only mobility; they conclude, that the energy, which produces the motion, cannot lie in the extension.

This conclusion leads them into another, which they regard as perfectly unavoidable. Matter, say they, is in itself entirely unactive, and deprived of any power, by which it may produce, or continue, or communicate motion: But since these effects are evident to our senses, and since the power, that produces them, must be placed somewhere, it must lie in the DEITY, or that divine being, who contains in his nature all excellency and perfection. It is the deity, therefore, who is the prime mover of the universe, and who not only first created matter, and gave it it’s original impulse, but likewise by a continued exertion of omnipotence, supports its existence, and successively bestows on it all those motions, and configurations, and qualities, with which it is endowed.

This opinion is certainly very curious, and well worth our attention; but it will appear superfluous to examine it in this place, if we reflect a moment on our present purpose in taking notice of it. We have established it as a principle, that as all ideas are derived from impressions, or some precedent perceptions, it is impossible we can have any idea of power and efficacy, unless some instances can be produced, wherein this power is perceived to exert itself. Now, as these instances can never be discovered in body, the Cartesians, proceeding upon their principle of innate ideas, have had recourse to a supreme spirit or deity, whom they consider as the only active being in the universe, and as the immediate cause of every alteration in matter. But the principle of innate ideas being allowed to be false, it follows, that the supposition of a deity can serve us in no stead, in accounting for that idea of agency, which we search for in vain in all the objects, which are presented to our senses, or which we are internally conscious of in our own minds. For if every idea be derived from an impression, the idea of a deity proceeds from the same origin; and if no impression, either of sensation or reflection, implies any force or efficacy, it is equally impossible to discover or even imagine any such active principle in the deity. Since these philosophers, therefore, have concluded, that matter cannot be endowed with any efficacious principle, because it is impossible to discover in it such a principle; the same course of reasoning should determine them to exclude it from the supreme being. Or if they esteem that opinion absurd and impious, as it really is, I shall tell them how they may avoid it; and that is, by concluding from the very first, that they have no adequate idea of power or efficacy in any object; since neither in body nor spirit, neither in superior nor inferior natures, are they able to discover one single instance of it.

The same conclusion is unavoidable upon the hypothesis of those, who maintain the efficacy of second causes, and attribute a derivative, but a real power and energy to matter. For as they confess, that this energy lies not in any of the known qualities of matter, the difficulty still remains concerning the origin of its idea. If we have really an idea of power, we may attribute power to an unknown quality: But as it is impossible, that that idea can be derived from such a quality, and as there is nothing in known qualities, which can produce it; it follows that we deceive ourselves, when we imagine we are possest of any idea of this kind, after the manner we commonly understand it. All ideas are derived from, and represent impressions. We never have any impression, that contains any power or efficacy. We never therefore have any idea of power.

Some have asserted, that we feel an energy, or power, in our own mind; and that having in this manner acquired the idea of power, we transfer that quality to matter, where we are not able immediately to discover it. The motions of our body, and the thoughts and sentiments of our mind, (say they) obey the will; nor do we seek any farther to acquire a just notion of force or power. But to convince us how fallacious this reasoning is, we need only consider, that the will being here considered as a cause, has no more a discoverable connexion with its effects, than any material cause has with its proper effect. So far from perceiving the connexion betwixt an act of volition, and a motion of the body; it is allowed that no effect is more inexplicable from the powers and essence of thought and matter. Nor is the empire of the will over our mind more intelligible. The effect is there distinguishable and separable from the cause, and coued not be foreseen without the experience of their constant conjunction. We have command over our mind to a certain degree, but beyond that, lose all empire over it: And it is evidently impossible to fix any precise bounds to our authority, where we consult not experience. In short, the actions of the mind are, in this respect, the same with those of matter. We perceive only their constant conjunction; nor can we ever reason beyond it. No internal impression has an apparent energy, more than external objects have. Since, therefore, matter is confessed by philosophers to operate by an unknown force, we should in vain hope to attain an idea of force by consulting our own minds.8

8 The same imperfection attends our ideas of the Deity; but this can have no effect either on religion or morals. The order of the universe proves an omnipotent mind; that is, a mind whose wili is CONSTANTLY ATTENDED with the obedience of every creature and being. Nothing more is requisite to give a foundation to all the articles of religion, nor is it necessary we should form a distinct idea of the force and energy of the supreme Being.

It has been established as a certain principle, that general or abstract ideas are nothing but individual ones taken in a certain light, and that, in reflecting on any object, it is as impossible to exclude from our thought all particular degrees of quantity and quality as from the real nature of things. If we be possest, therefore, of any idea of power in general, we must also be able to conceive some particular species of it; and as power cannot subsist alone, but is always regarded as an attribute of some being or existence, we must be able to place this power in some particular being, and conceive that being as endowed with a real force and energy, by which such a particular effect necessarily results from its operation. We must distinctly and particularly conceive the connexion betwixt the cause and effect, and be able to pronounce, from a simple view of the one, that it must be followed or preceded by the other. This is the true manner of conceiving a particular power in a particular body: and a general idea being impossible without an individual; where the latter is impossible, it is certain the former can never exist. Now nothing is more evident, than that the human mind cannot form such an idea of two objects, as to conceive any connexion betwixt them, or comprehend distinctly that power or efficacy, by which they are united. Such a connexion would amount to a demonstration, and would imply the absolute impossibility for the one object not to follow, or to be conceived not to follow upon the other: Which kind of connexion has already been rejected in all cases. If any one is of a contrary opinion, and thinks he has attained a notion of power in any particular object, I desire he may point out to me that object. But till I meet with such-a-one, which I despair of, I cannot forbear concluding, that since we can never distinctly conceive how any particular power can possibly reside in any particular object, we deceive ourselves in imagining we can form any such general idea.

Thus upon the whole we may infer, that when we talk of any being, whether of a superior or inferior nature, as endowed with a power or force, proportioned to any effect; when we speak of a necessary connexion betwixt objects, and suppose, that this connexion depends upon an efficacy or energy, with which any of these objects are endowed; in all these expressions, so applied, we have really no distinct meaning, and make use only of common words, without any clear and determinate ideas. But as it is more probable, that these expressions do here lose their true meaning by being wrong applied, than that they never have any meaning; it will be proper to bestow another consideration on this subject, to see if possibly we can discover the nature and origin of those ideas, we annex to them.

Suppose two objects to be presented to us, of which the one is the cause and the other the effect; it is plain, that from the simple consideration of one, or both these objects we never shall perceive the tie by which they are united, or be able certainly to pronounce, that there is a connexion betwixt them. It is not, therefore, from any one instance, that we arrive at the idea of cause and effect, of a necessary connexion of power, of force, of energy, and of efficacy. Did we never see any but particular conjunctions of objects, entirely different from each other, we should never be able to form any such ideas.

But again; suppose we observe several instances, in which the same objects are always conjoined together, we immediately conceive a connexion betwixt them, and begin to draw an inference from one to another. This multiplicity of resembling instances, therefore, constitutes the very essence of power or connexion, and is the source from which the idea of it arises. In order, then, to understand the idea of power, we must consider that multiplicity; nor do I ask more to give a solution of that difficulty, which has so long perplexed us. For thus I reason. The repetition of perfectly similar instances can never alone give rise to an original idea, different from what is to be found in any particular instance, as has been observed, and as evidently follows from our fundamental principle, that all ideas are copyed from impressions. Since therefore the idea of power is a new original idea, not to be found in any one instance, and which yet arises from the repetition of several instances, it follows, that the repetition alone has not that effect, but must either discover or produce something new, which is the source of that idea. Did the repetition neither discover nor produce anything new, our ideas might be multiplyed by it, but would not be enlarged above what they are upon the observation of one single instance. Every enlargement, therefore, (such as the idea of power or connexion) which arises from the multiplicity of similar instances, is copyed from some effects of the multiplicity, and will be perfectly understood by understanding these effects. Wherever we find anything new to be discovered or produced by the repetition, there we must place the power, and must never look for it in any other object.

But it is evident, in the first place, that the repetition of like objects in like relations of succession and contiguity discovers nothing new in any one of them: since we can draw no inference from it, nor make it a subject either of our demonstrative or probable reasonings;[Sect. 6.] as has been already proved. Nay suppose we coued draw an inference, it would be of no consequence in the present case; since no kind of reasoning can give rise to a new idea, such as this of power is; but wherever we reason, we must antecedently be possest of clear ideas, which may be the objects of our reasoning. The conception always precedes the understanding; and where the one is obscure, the other is uncertain; where the one fails, the other must fail also.

Secondly, It is certain that this repetition of similar objects in similar situations produces nothing new either in these objects, or in any external body. For it will readily be allowed, that the several instances we have of the conjunction of resembling causes and effects are in themselves entirely independent, and that the communication of motion, which I see result at present from the shock of two billiard-balls, is totally distinct from that which I saw result from such an impulse a twelve-month ago. These impulses have no influence on each other. They are entirely divided by time and place; and the one might have existed and communicated motion, though the other never had been in being.

There is, then, nothing new either discovered or produced in any objects by their constant conjunction, and by the uninterrupted resemblance of their relations of succession and contiguity. But it is from this resemblance, that the ideas of necessity, of power, and of efficacy, are derived. These ideas, therefore, represent not anything, that does or can belong to the objects, which are constantly conjoined. This is an argument, which, in every view we can examine it, will be found perfectly unanswerable. Similar instances are still the first source of our idea of power or necessity; at the same time that they have no influence by their similarity either on each other, or on any external object. We must, therefore, turn ourselves to some other quarter to seek the origin of that idea.

Though the several resembling instances, which give rise to the idea of power, have no influence on each other, and can never produce any new quality in the object, which can be the model of that idea, yet the observation of this resemblance produces a new impression in the mind, which is its real model. For after we have observed the resemblance in a sufficient number of instances, we immediately feel a determination of the mind to pass from one object to its usual attendant, and to conceive it in a stronger light upon account of that relation. This determination is the only effect of the resemblance; and therefore must be the same with power or efficacy, whose idea is derived from the resemblance. The several instances of resembling conjunctions lead us into the notion of power and necessity. These instances are in themselves totally distinct from each other, and have no union but in the mind, which observes them, and collects their ideas. Necessity, then, is the effect of this observation, and is nothing but an internal impression of the mind, or a determination to carry our thoughts from one object to another. Without considering it in this view, we can never arrive at the most distant notion of it, or be able to attribute it either to external or internal objects, to spirit or body, to causes or effects.

The necessary connexion betwixt causes and effects is the foundation of our inference from one to the other. The foundation of our inference is the transition arising from the accustomed union. These are, therefore, the same.

The idea of necessity arises from some impression. There is no impression conveyed by our senses, which can give rise to that idea. It must, therefore, be derived from some internal impression, or impression of reflection. There is no internal impression, which has any relation to the present business, but that propensity, which custom produces, to pass from an object to the idea of its usual attendant. This therefore is the essence of necessity. Upon the whole, necessity is something, that exists in the mind, not in objects; nor is it possible for us ever to form the most distant idea of it, considered as a quality in bodies. Either we have no idea of necessity, or necessity is nothing but that determination of the thought to pass from causes to effects, and from effects to causes, according to their experienced union.

Thus as the necessity, which makes two times two equal to four, or three angles of a triangle equal to two right ones, lies only in the act of the understanding, by which we consider and compare these ideas; in like manner the necessity or power, which unites causes and effects, lies in the determination of the mind to pass from the one to the other. The efficacy or energy of causes is neither placed in the causes themselves, nor in the deity, nor in the concurrence of these two principles; but belongs entirely to the soul, which considers the union of two or more objects in all past instances. It is here that the real power of causes is placed along with their connexion and necessity.

I am sensible, that of all the paradoxes, which I have had, or shall hereafter have occasion to advance in the course of this treatise, the present one is the most violent, and that it is merely by dint of solid proof and reasoning I can ever hope it will have admission, and overcome the inveterate prejudices of mankind. Before we are reconciled to this doctrine, how often must we repeat to ourselves, that the simple view of any two objects or actions, however related, can never give us any idea, of power, or of a connexion betwixt them: that this idea arises from the repetition of their union: that the repetition neither discovers nor causes any thing in the objects, but has an influence only on the mind, by that customary transition it produces: that this customary transition is, therefore, the same with the power and necessity; which are consequently qualities of perceptions, not of objects, and are internally felt by the soul, and not perceivd externally in bodies? There is commonly an astonishment attending every thing extraordinary; and this astonishment changes immediately into the highest degree of esteem or contempt, according as we approve or disapprove of the subject. I am much afraid, that though the foregoing reasoning appears to me the shortest and most decisive imaginable; yet with the generality of readers the biass of the mind will prevail, and give them a prejudice against the present doctrine.

This contrary biass is easily accounted for. It is a common observation, that the mind has a great propensity to spread itself on external objects, and to conjoin with them any internal impressions, which they occasion, and which always make their appearance at the same time that these objects discover themselves to the senses. Thus as certain sounds and smells are always found to attend certain visible objects, we naturally imagine a conjunction, even in place, betwixt the objects and qualities, though the qualities be of such a nature as to admit of no such conjunction, and really exist no where. But of this more fully hereafter [Part IV, Sect. 5.]. Mean while it is sufficient to observe, that the same propensity is the reason, why we suppose necessity and power to lie in the objects we consider, not in our mind that considers them; notwithstanding it is not possible for us to form the most distant idea of that quality, when it is not taken for the determination of the mind, to pass from the idea of an object to that of its usual attendant.

But though this be the only reasonable account we can give of necessity, the contrary notion if; so riveted in the mind from the principles above-mentioned, that I doubt not but my sentiments will be treated by many as extravagant and ridiculous. What! the efficacy of causes lie in the determination of the mind! As if causes did not operate entirely independent of the mind, and would not continue their operation, even though there was no mind existent to contemplate them, or reason concerning them. Thought may well depend on causes for its operation, but not causes on thought. This is to reverse the order of nature, and make that secondary, which is really primary, To every operation there is a power proportioned; and this power must be placed on the body, that operates. If we remove the power from one cause, we must ascribe it to another: But to remove it from all causes, and bestow it on a being, that is no ways related to the cause or effect, but by perceiving them, is a gross absurdity, and contrary to the most certain principles of human reason.

I can only reply to all these arguments, that the case is here much the same, as if a blind man should pretend to find a great many absurdities in the supposition, that the colour of scarlet is not the same with the sound of a trumpet, nor light the same with solidity. If we have really no idea of a power or efficacy in any object, or of any real connexion betwixt causes and effects, it will be to little purpose to prove, that an efficacy is necessary in all operations. We do not understand our own meaning in talking so, but ignorantly confound ideas, which are entirely distinct from each other. I am, indeed, ready to allow, that there may be several qualities both in material and immaterial objects, with which we are utterly unacquainted; and if we please to call these POWER or EFFICACY, it will be of little consequence to the world. But when, instead of meaning these unknown qualities, we make the terms of power and efficacy signify something, of which we have a clear idea, and which is incompatible with those objects, to which we apply it, obscurity and error begin then to take place, and we are led astray by a false philosophy. This is the case, when we transfer the determination of the thought to external objects, and suppose any real intelligible connexion betwixt them; that being a quality, which can only belong to the mind that considers them.

As to what may be said, that the operations of nature are independent of our thought and reasoning, I allow it; and accordingly have observed, that objects bear to each other the relations of contiguity and succession: that like objects may be observed in several instances to have like relations; and that all this is independent of, and antecedent to the operations of the understanding. But if we go any farther, and ascribe a power or necessary connexion to these objects; this is what we can never observe in them, but must draw the idea of it from what we feel internally in contemplating them. And this I carry so far, that I am ready to convert my present reasoning into an instance of it, by a subtility, which it will not be difficult to comprehend.

When any object is presented to us, it immediately conveys to the mind a lively idea of that object, which is usually found to attend it; and this determination of the mind forms the necessary connexion of these objects. But when we change the point of view, from the objects to the perceptions; in that case the impression is to be considered as the cause, and the lively idea as the effect; and their necessary connexion is that new determination, which we feel to pass from the idea of the one to that of the other. The uniting principle among our internal perceptions is as unintelligible as that among external objects, and is not known to us any other way than by experience. Now the nature and effects of experience have been already sufficiently examined and explained. It never gives us any insight into the internal structure or operating principle of objects, but only accustoms the mind to pass from one to another.

It is now time to collect all the different parts of this reasoning, and by joining them together form an exact definition of the relation of cause and effect, which makes the subject of the present enquiry. This order would not have been excusable, of first examining our inference from the relation before we had explained the relation itself, had it been possible to proceed in a different method. But as the nature of the relation depends so much on that of the inference, we have been obliged to advance in this seemingly preposterous manner, and make use of terms before we were able exactly to define them, or fix their meaning. We shall now correct this fault by giving a precise definition of cause and effect.

There may two definitions be given of this relation, which are only different, by their presenting a different view of the same object, and making us consider it either as a philosophical or as a natural relation; either as a comparison of two ideas, or as an association betwixt them. We may define a CAUSE to be An object precedent and contiguous to another, and where all the objects resembling the former are placed in like relations of precedency and contiguity to those objects that resemble the latter. I If this definition be esteemed defective, because drawn from objects foreign to the cause, we may substitute this other definition in its place, viz. A CAUSE is an object precedent and contiguous to another, and so united with it, that the idea, of the one determines the mind to form the idea of the other, and the impression of the one to form a more lively idea of the other. 2 should this definition also be rejected for the same reason, I know no other remedy, than that the persons, who express this delicacy, should substitute a juster definition in its place. But for my part I must own my incapacity for such an undertaking. When I examine with the utmost accuracy those objects, which are commonly denominated causes and effects, I find, in considering a single instance, that the one object is precedent and contiguous to the other; and in inlarging my view to consider several instances, I find only, that like objects are constantly placed in like relations of succession and contiguity. Again, when I consider the influence of this constant conjunction, I perceive, that such a relation can never be an object of reasoning, and can never operate upon the mind, but by means of custom, which determines the imagination to make a transition from the idea of one object to that of its usual attendant, and from the impression of one to a more lively idea of the other. However extraordinary these sentiments may appear, I think it fruitless to trouble myself with any farther enquiry or reasoning upon the subject, but shall repose myself on them as on established maxims.

It will only be proper, before we leave this subject, to draw some corrollaries from it, by which we may remove several prejudices and popular errors, that have very much prevailed in philosophy. First, We may learn from the foregoing, doctrine, that all causes are of the same kind, and that in particular there is no foundation for that distinction, which we sometimes make betwixt efficient causes and causes sine qua non; or betwixt efficient causes, and formal, and material, and exemplary, and final causes. For as our idea of efficiency is derived from the constant conjunction of two objects, wherever this is observed, the cause is efficient; and where it is not, there can never be a cause of any kind. For the same reason we must reject the distinction betwixt cause and occasion, when supposed to signify any thing essentially different from each other. If constant conjunction be implyed in what we call occasion, it is a real cause. If not, it is no relation at all, and cannot give rise to any argument or reasoning.

Secondly, The same course of reasoning will make us conclude, that there is but one kind of necessity, as there is but one kind of cause, and that the common distinction betwixt moral and physical necessity is without any foundation in nature. This clearly appears from the precedent explication of necessity. It is the constant conjunction of objects, along with the determination of the mind, which constitutes a physical necessity: And the removal of these is the same thing with chance. As objects must either be conjoined or not, and as the mind must either be determined or not to pass from one object to another, it is impossible to admit of any medium betwixt chance and an absolute necessity. In weakening this conjunction and determination you do not change the nature of the necessity; since even in the operation of bodies, these have different degrees of constancy and force, without producing a different species of that relation.

The distinction, which we often make betwixt POWER and the EXERCISE of it, is equally without foundation.

Thirdly, We may now be able fully to overcome all that repugnance, which it is so natural for us to entertain against the foregoing reasoning, by which we endeavoured to prove, that the necessity of a cause to every beginning of existence is not founded on any arguments either demonstrative or intuitive. Such an opinion will not appear strange after the foregoing definitions. If we define a cause to be an object precedent and contiguous to another, and where all the objects resembling the farmer are placed in a like relation of .priority and contiguity to those objects, that resemble the latter; we may easily conceive, that there is no absolute nor metaphysical necessity, that every beginning of existence should be attended with such an object. If we define a cause to be, AN OBJECT PRECEDENT AND CONTIGUOUS TO ANOTHER, AND SO UNITED WITH IT IN THE IMAGINATION, THAT THE IDEA OF THE ONE DETERMINES THE MIND TO FORM THE IDEA OF THE OTHER, AND THE IMPRESSION OF THE ONE TO FORM A MORE LIVELY IDEA OF THE OTHER; we shall make still less difficulty of assenting to this opinion. Such an influence on the mind is in itself perfectly extraordinary and incomprehensible; nor can we be certain of its reality, but from experience and observation.

I shall add as a fourth corrollary that we can never have reason to believe that any object exists, of which we cannot form an idea. For as all our reasonings concerning existence are derived from causation, and as all our reasonings concerning causation are derived from the experienced conjunction of objects, not from any reasoning or reflection, the same experience must give us a notion of these objects, and must remove all mystery from our conclusions. This is so evident, that it would scarce have merited our attention, were it not to obviate certain objections of this kind, which might arise against the following reasonings concerning matter and substance. I need not observe, that a full knowledge of the object is not requisite, but only of those qualities of it, which we believe to exist.

From:

Hume, David. A Treatise of Human Nature. Ed. L.A Selby-Bigge. Oxford: Clarendon Press, 1979.

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