Pirates & Revolutionaries: Hume, A Treatise of Human Nature, Book 1, Part 2, Sect 3 "Of the Other Qualities of our Ideas of Space and Time," §§76-90

by Corry Shores
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[The following is summary, up to the end where I reproduce this section in full. My commentary is in brackets.]

David Hume

A Treatise of Human Nature

Book I: Of the Understanding

Part II: Of the Ideas of Space and Time

Section III: "Of the Other Qualities of our Ideas of Space and Time"

§76

Previously we discussed how all the ideas can be traced back to impressions. Thus impressions take precedence over ideas [see §17]. And also, all the ideas in our imagination first were given as impressions. This discovery alone has made a large contribution to many debates regarding our ideas. All our impressions are vividly clear. But often our ideas are obscure. We will apply this principle to our ideas of space and time.

§77

To explain how we develop the idea of extension, Hume has us conduct a demonstration. We see with our eyes open many things around us. We then close our eyes and consider the distances between these objects we just saw. By means of this impression, we obtain the idea of extension [compare to Bergson's closed-eye demonstration that explains how we obtain the qualitative feeling of motion, rather than its extensive properties.] So there are two possible kinds of impressions that can lead to the idea of extension:

1) visual impressions, or

2) internal impressions arising from sight impressions.

§78

We would like to determine more specifically what sorts of internal impressions may give rise to the notion of space. It does not seem that our passion, emotions, desires, or aversions could possibly lead to our notion of space. The only other possibility for the source of the idea of space is the senses. Our principle question is now, what sort of sensory impression produces the notion of space? (33-34)

§79

We see a table before us. We see its spatial extent. Hence, this image alone suffices to endow us with the idea of extension. So in this case, an impression appears to the senses. Then, we borrow from the impression the idea of its extension. And this borrowed idea now represents the impression of the table's extension.

However, our senses did not convey to us geometrical lines. Rather, they only gave us the impression of colored points that are found before us in a certain manner. Hume thinks we see no more than precisely what we see.

If the eye is sensible of any thing farther, I desire it may be pointed out to me. But if it be impossible to shew any thing farther, we may conclude with certainty, that the idea of extension is nothing but a copy of these colour'd points, and of the manner of their appearance. (34ab)

§80

Now imagine that the table we have seen is purple. That means every time the idea repeats, it will not only retain the extensive proportions, but also the purple color. Then we see many other objects of a whole variety of colors and shapes. On the one hand, when we see purple objects no matter their shape, we have a tendency perhaps to recall the purple table. But on the other hand, we also see objects of different colors sharing similar proportions as the purple table. In those cases, despite the color differences, we will still have the tendency to recall the purple table. Hence in this way we regard extension as distinct from color. But there is never an "abstract" or "general" idea that is like a category for extension. However, when we hear the word 'purple' our minds will tend to recall any of the purple objects no matter their form. This is because we have developed the habit of associating this word with any of those impressions.

All abstract ideas are really nothing but particular ones, consider'd in a certain light; but being annexed to general terms, they are able to represent a vast variety, and to comprehend objects, which, as they are alike in some particulars, are in others vastly wide of each other. (34d)

§81

Our great variety of

a) impressions of reflections and

b) impressions of sensations

are given to us in succession. From this succession we obtain the idea of time. (34-35) Every visual impression will lend to our idea of space. But any impression whatsoever will contribute to our idea of time. Any specific impression will cause us to tend towards recalling those in succession with it. Hence our idea of time is represented by some particular individual idea.

§82

from the disposition of visible and tangible objects we receive the idea of space, so from the succession of ideas and impressions we form the idea of time. (35b)

To have the idea of time, we must have the tendency of recalling other successive impressions and ideas. But this means we must first have some impression or idea that evokes that association. Hence it is not possible "for time alone ever to make its appearance, or be taken notice of by the mind." (35b)

Someone sleeping is having no succession of thoughts. So he has no sense of time. Or, someone occupied with just one thought is as well insensible of time. Now, if someone has many different thoughts rapidly succeed one another in a given duration, then time will seem to move quickly for him. But if in that same duration he has only a few impressions succeeding each other, then time will seem slower for him. Locke even says that we have limits to how fast or how slow we may receive impressions. Consider when in the darkness we take a red-hot coal and swing it around in circles. We no longer see the coal. Rather we see a red circle. This is because the amber is moving faster than we are able to have impressions of it.

If you wheel about a burning coal with rapidity, it will present to the senses an image of a circle of fire; nor will there seem to be any interval of time betwixt its revolutions; meerly because 'tis impossible for our perceptions to succeed each other with the same rapidity, that motion may be communicated to external objects. (35b)

So we sense motion whenever something moves faster than our ability to have successive impressions of it. And, whenever we have no successive impressions, we as well have no sense of time, even though there is a succession continuing in the world around us. Thus,

time cannot make its appearance to the mind, either alone, or attended with a steady unchangeable object, but is always discover'd by some perceivable succession of changeable objects. (35cd)

§83

Hume will now offer an argument to make the above point absolutely convincing.

We perceive longer and shorter durations. Thus we know that time consists of parts. Also, we distinguish duration from extension. We do so by means of a distinguishing quality. What distinguishes extension is that its parts co-exist. Hence we know that durations' parts do not co-exist. Thus time is composed of non-coexisting parts.

Now, if we saw an object that does not change, then it will never produce a different impression. Hence we will not perceive a succession. Instead, all of our impressions of it will co-exist. For, we do not sense them succeeding one another. Thus an unchanging object will not give us the idea of time. Rather, we may only obtain the idea of time from a succession of changing objects. And when time first appears to us, it cannot be severed from the changing succession that brings it about. (36a)

§84

So we know now that when time first appears to us, it is conjoined with a succession of changing objects. And when there is not a succession of changing objects, we will not notice time. Now we ask, is it possible to conceive time without also conceiving a succession of objects? And are successions the only way we may form a distinct idea of time?

§85

So we want to know if we can have the idea of time distinct from the successive impressions that first produce our sense of duration. We know that when things are different, they are distinguishable. And all distinguishable things may be separated. For, if things are different, they may be conceived apart [See §47 for more on this principle.] But, if things are not different, then they are not distinguishable. And if they are not distinguishable, they cannot be separated.

Imagine you hear a flute play five notes. You perceive the notes. And by means of their succession, you perceive time. But you do not thereby have six impressions: five notes and one time impression. And when we reflect on our impressions of these notes, we also will obtain a notion of time. Yet still we do not thereby obtain it as an additional impression.

The idea of time is not deriv'd from a particular impression mix'd up with others, and plainly distinguishable from them; but arises altogether from the manner, in which impressions appear to the mind, without making one of the number. (36c)

These five sounds making their appearance in this particular manner, excite no emotion in the mind, nor produce an affection of any kind, which being observ'd by it can give rise to a new idea. (36-37)

But we need such an additional emotion or affection in order to produce the extra impression of time. Our minds notice just the manner that the impressions succeeded each other. This way it may associate it with other successions.

We said above that things which cannot be separated or distinguished are no different. Hence there is no difference between the successions and our idea of time. Thus also, we can only conceive time when there are objects. Time cannot be conceived by itself. For it does not appear as a "primary distinct impression." It is no more than different ideas, impressions, or objects related in a certain manner, that is, by succession. (37a)

§86

Some argue that duration applies to unchanging objects. But we just noted that the idea of duration only results from a succession of changeable objects. We cannot derive it from things that do not change.

Now, if we cannot derive a property from an object, we as well cannot rightly apply that property to it. We cannot derive duration from an unchanging object. Hence we cannot consider unchanging things to have duration.

We obtain ideas from impressions. These ideas represent their proper impressions. It is possible that we might use one idea to represent some other impression. But we can only do so by means of a fiction. Later in section 5 we will consider the fiction that allows us to apply the idea of time to the unchangeable. This error causes us to consider duration as a measure of rest as well as motion. (37d)

§87

We have discussed our ideas of time and space. We derive these ideas from our impressions. We found that a doctrine regarding the ideas of space and time is that they are not distinguishable from their proper impressions. This doctrine is established by another "very decisive argument." It is based on this principle: our ideas of space and time are compounded of parts, which are indivisible. Hume will now examine that argument. (38a)

§87

In §67, we built-up the idea of extension from simple smaller ideas. As distinguishable, each of these ideas are also separable [as we noted in §47]. We will now examine one of these simple ideas of extension so to determine its nature and qualities.

§87

We know that extended things have parts. So the idea of extension has parts. That is to say, it is a compound idea made-up of simple ideas. But none of extension's simple ideas themselves have any parts. So no one of extension's simple ideas by itself qualifies as an idea of extension.

We also know that the compound idea of extension is a real idea. So it cannot be made up of ideas that are nothing. Also, we know that extension's simple ideas are not themselves ideas of extension. But they also cannot be nothing either.

These simple ideas must be of indivisible units. Otherwise we would obtain Zeno's paradoxes. [Again, see §67.] So Hume wonders, what is our idea of a simple an indivisible point? We are not asking a mathematical question about the nature of mathematical points. Rather we are wondering about the nature of their ideas. No one has considered this question yet, so Hume's answer will seem somewhat new. (38c)

§88

Things that are neither visible nor tangible do not appear extended to us. So we obtain the idea of space by means of two senses: sight and touch.

We know that extensions are made of parts. Also, the compound sense impressions that give us objects' extensivity is also made of parts. These "lesser impression" are indivisible to the eye or tactile feeling. [see §65 for Hume's ink-spot demonstration.] These indivisible impressions are of "atoms or corpuscles endow'd with colour and solidity." (38c) And, we must preserve the idea of their color or tangibility in order for our imagination to comprehend them.

There is nothing but the idea of their colour or tangibility which can render them conceivable by the mind. (38d)

If we remove the ideas of these sensible qualities, "they are utterly annihilated to the thought or imagination." (38-39)

§89

If something holds for the parts, then it holds for the whole as well. [contrast this principle to the principle of emergentism which might say the parts have properties the whole does not, and vice versa.] Now, we have sensible impressions of an extended object's indivisible parts. If our impressions of the parts do not give us impressions of their color or tangibility, then they will not convey any ideas to us. And, our idea of extension is composed of these points. So if the parts give us no ideas, the we cannot have an idea of extension.

However, we do have an idea of extension. Thus its parts must exists. So these must be colored and tangible.

We have therefore no idea of space or extension, but when we regard it as an object either of our sight or feeling. (39ab)

§90

So the indivisible parts of extension must be filled with some real object or existence. We will find that this holds as well for time. The indivisible moments' succession both forms duration and renders it mentally conceivable. (39b)

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From Hume's original text:

PART II. OF THE IDEAS OF SPACE AND TIME
Sect. iii. Of the Other Qualities of Our Idea of Space and Time.
No discovery coued have been made more happily for deciding all controversies concerning ideas, than that abovementioned, that impressions always take the precedency of them, and that every idea, with which the imagination is furnished, first makes its appearance in a correspondent impression. These latter perceptions are all so clear and evident, that they admit of no controversy; though many of our ideas are so obscure, that it is almost impossible even for the mind, which forms them, to tell exactly their nature and composition. Let us apply this principle, in order to discover farther the nature of our ideas of space and time.
Upon opening my eyes, and turning them to the surrounding objects, I perceive many visible bodies; and upon shutting them again, and considering the distance betwixt these bodies, I acquire the idea of extension. As every idea is derived from some impression, which is exactly similar to it, the impressions similar to this idea of extension, must either be some sensations derived from the sight, or some internal impressions arising from these sensations.
Our internal impressions are our passions, emotions, desires and aversions; none of which, I believe, will ever be asserted to be the model, from which the idea of space is derived. There remains therefore nothing but the senses, which can convey to us this original impression. Now what impression do oar senses here convey to us? This is the principal question, and decides without appeal concerning the nature of the idea.
The table before me is alone sufficient by its view to give me the idea of extension. This idea, then, is borrowed from, and represents some impression, which this moment appears to the senses. But my senses convey to me only the impressions of coloured points, disposed in a, certain manner. If the eye is sensible of any thing farther, I desire it may be pointed out to me. But if it be impossible to shew any thing farther, we may conclude with certainty, that the idea of extension is nothing but a copy of these coloured points, and of the manner of their appearance.
Suppose that in the extended object, or composition of coloured points, from which we first received the idea of extension, the points were of a purple colour; it follows, that in every repetition of that idea we would not only place the points in the same order with respect to each other, but also bestow on them that precise colour, with which alone we are acquainted. But afterwards having experience of the other colours of violet, green, red, white, black, and of all the different compositions of these, and finding a resemblance in the disposition of coloured points, of which they are composed, we omit the peculiarities of colour, as far as possible, and found an abstract idea merely on that disposition of points, or manner of appearance, in which they agree. Nay even when the resemblance is carryed beyond the objects of one sense, and the impressions of touch are found to be Similar to those of sight in the disposition of their parts; this does not hinder the abstract idea from representing both, upon account of their resemblance. All abstract ideas are really nothing but particular ones, considered in a certain light; but being annexed to general terms, they are able to represent a vast variety, and to comprehend objects, which, as they are alike in some particulars, are in others vastly wide of each other.
The idea of time, being derived from the succession of our perceptions of every kind, ideas as well as impressions, and impressions of reflection as well as of sensations will afford us an instance of an abstract idea, which comprehends a still greater variety than that of space, and yet is represented in the fancy by some particular individual idea of a determinate quantity and quality.
As it is from the disposition of visible and tangible objects we receive the idea of space, so from the succession of ideas and impressions we form the idea of time, nor is it possible for time alone ever to make its appearance, or be taken notice of by the mind. A man in a sound sleep, or strongly occupyed with one thought, is insensible of time; and according as his perceptions succeed each other with greater or less rapidity, the same duration appears longer or shorter to his imagination. It has been remarked by a great philosopher, that our perceptions have certain bounds in this particular, which are fixed by the original nature and constitution of the mind, and beyond which no influence of external objects on the senses is ever able to hasten or retard our thought. If you wheel about a burning coal with rapidity, it will present to the senses an image of a circle of fire; nor will there seem to be any interval of time betwixt its revolutions; meerly because it is impossible for our perceptions to succeed each other with the same rapidity, that motion may be communicated to external objects. Wherever we have no successive perceptions, we have no notion of time, even though there be a real succession in the objects. From these phenomena, as well as from many others, we may conclude, that time cannot make its appearance to the mind, either alone, or attended with a steady unchangeable object, but is always discovered some PERCEIVABLE succession of changeable objects.
To confirm this we may add the following argument, which to me seems perfectly decisive and convincing. It is evident, that time or duration consists of different parts: For otherwise we coued not conceive a longer or shorter duration. It is also evident, that these parts are not co-existent: For that quality of the co-existence of parts belongs to extension, and is what distinguishes it from duration. Now as time is composed of parts, that are not coexistent: an unchangeable object, since it produces none but coexistent impressions, produces none that can give us the idea of time; and consequently that idea must be derived from a succession of changeable objects, and time in its first appearance can never be severed from such a succession.
Having therefore found, that time in its first appearance to the mind is always conjoined with a succession of changeable objects, and that otherwise it can never fall under our notice, we must now examine whether it can be conceived without our conceiving any succession of objects, and whether it can alone form a distinct idea in the imagination.
In order to know whether any objects, which are joined in impression, be inseparable in idea, we need only consider, if they be different from each other; in which case, it is plain they may be conceived apart. Every thing, that is different is distinguishable: and everything, that is distinguishable, may be separated, according to the maxims above-explained. If on the contrary they be not different, they are not distinguishable: and if they be not distinguishable, they cannot be separated. But this is precisely the case with respect to time, compared with our successive perceptions. The idea of time is not derived from a particular impression mixed up with others, and plainly distinguishable from them; but arises altogether from the manner, in which impressions appear to the mind, without making one of the number. Five notes played on a flute give us the impression and idea of time; though time be not a sixth impression, which presents itself to the hearing or any other of the senses. Nor is it a sixth impression, which the mind by reflection finds in itself. These five sounds making their appearance in this particular manner, excite no emotion in the mind, nor produce an affection of any kind, which being observed by it can give rise to a new idea. For that is necessary to produce a new idea of reflection, nor can the mind, by revolving over a thousand times all its ideas of sensation, ever extract from them any new original idea, unless nature has so framed its faculties, that it feels some new original impression arise from such a contemplation. But here it only takes notice of the manner, in which the different sounds make their appearance; and that it may afterwards consider without considering these particular sounds, but may conjoin it with any other objects. The ideas of some objects it certainly must have, nor is it possible for it without these ideas ever to arrive at any conception of time; which since it, appears not as any primary distinct impression, can plainly be nothing but different ideas, or impressions, or objects disposed in a certain manner, that is, succeeding each other.
I know there are some who pretend, that the idea of duration is applicable in a proper sense to objects, which are perfectly unchangeable; and this I take to be the common opinion of philosophers as well as of the vulgar. But to be convinced of its falsehood we need but reflect on the foregoing conclusion, that the idea of duration is always derived from a succession of changeable objects, and can never be conveyed to the mind by any thing stedfast and unchangeable. For it inevitably follows from thence, that since the idea of duration cannot be derived from such an object, it can never-in any propriety or exactness be applied to it, nor can any thing unchangeable be ever said to have duration. Ideas always represent the Objects or impressions, from which they are derived, and can never without a fiction represent or be applied to any other. By what fiction we apply the idea of time, even to what is unchangeable, and suppose, as is common, that duration is a measure of rest as well as of motion, we shall consider [Sect 5.] afterwards.
There is another very decisive argument, which establishes the present doctrine concerning our ideas of space and time, and is founded only on that simple principle, that our ideas of them are compounded of parts, which are indivisible. This argument may be worth the examining.
Every idea, that is distinguishable, being also separable, let us take one of those simple indivisible ideas, of which the compound one of extension is formed, and separating it from all others, and considering it apart, let us form a judgment of its nature and qualities.
It is plain it is not the idea of extension. For the idea of extension consists of parts; and this idea, according to t-he supposition, is perfectly simple and indivisible. Is it therefore nothing? That is absolutely impossible. For as the compound idea of extension, which is real, is composed of such ideas; were these so many non-entities, there would be a real existence composed of non-entities; which is absurd. Here therefore I must ask, What is our idea of a simple and indivisible point? No wonder if my answer appear somewhat new, since the question itself has scarce ever yet been thought of. We are wont to dispute concerning the nature of mathematical points, but seldom concerning the nature of their ideas.
The idea of space is conveyed to the mind by two senses, the sight and touch; nor does anything ever appear extended, that is not either visible or tangible. That compound impression, which represents extension, consists of several lesser impressions, that are indivisible to the eye or feeling, and may be called impressions of atoms or corpuscles endowed with colour and solidity. But this is not all. It is not only requisite, that these atoms should be coloured or tangible, in order to discover themselves to our senses; it is also necessary we should preserve the idea of their colour or tangibility in order to comprehend them by our imagination. There is nothing but the idea of their colour or tangibility, which can render them conceivable by the mind. Upon the removal of the ideas of these sensible qualities, they are utterly annihilated to the thought or imagination.
Now such as the parts are, such is the whole. If a point be not considered as coloured or tangible, it can convey to us no idea; and consequently the idea of extension, which is composed of the ideas of these points, can never possibly exist. But if the idea of extension really can exist, as we are conscious it does, its parts must also exist; and in order to that, must be considered as coloured or tangible. We have therefore no idea of space or extension, but when we regard it as an object either of our sight or feeling.
The same reasoning will prove, that the indivisible moments of time must be filled with some real object or existence, whose succession forms the duration, and makes it be conceivable by the mind.