Pirates & Revolutionaries: Hume, A Treatise of Human Nature, Book 1, Part 3, Sect 5 " Of the Impressions of the Senses and Memory" §§196-203

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. Paragraph headings are my own.]

David Hume

A Treatise of Human Nature

Book I: Of the Understanding

Part III: Of Knowledge and Probability

Section V: Of the Impressions of the Senses and Memory

§196 Heterogeneity and Causal Procedures

Previously we saw how we infer effects from causes. We noted that there was nothing inherent to either the cause or the effect that would necessitate their causal relation. In fact, they can be very different sorts of things. But so long as we causally associate one with the other, their differences no longer matter so much. As Hume writes:

In this kind of reasoning, then, from causation, we employ materials, which are of a mixed and heterogeneous nature, and which, however connected, are yet essentially different from each other. (84bc emphasis mine)

We firstly have sense impressions. These produce ideas of things perceived. We then causally connect these ideas with impressions from our memory or senses. However, the sense or memory impressions might be found in presupposed causal relations [see §193 for more details on the causal chains terminating in sense impressions.]

Hume will now need to explain three things:

1) The original impressions that produce ideas.

2) The transition to the idea of the connected cause and effect.

3) The nature and qualities of that idea.

§197 Our Aim is Modest:

Let's Just Explain What We Can Know

We have sensations. They impress upon us. We would need to indulge in highly theoretical speculations in order to explain what is doing the impressing, and how it does its impressing. Thus Hume says that the ultimate cause for these sense impressions is beyond our abilities to understand.

As to those impressions, which arise from the senses, their ultimate cause is, in my opinion, perfectly inexplicable by human reason, and it will always be impossible to decide with certainty, whether they arise immediately from the object, or are produced by the creative power of the mind, or are derived from the author of our being. (84cd)

But, Hume only wants to explain those aspects of our mental life that we can direct access. So he does not regard these theoretical questions to be pertinent to his presentation. We only need to rest with the fact that we may determine the truth or falsity of our perceptions by means of their coherence with each other.

We may draw inferences from the coherence of our perceptions, whether they be true or false; whether they represent nature justly, or be mere illusions of the senses. (84d)

§198 Vivid Memories and Faint Fancies

We will want to distinguish the memory from the imagination. Both these faculties borrow their simple ideas from impressions. And neither can go beyond these impressions. So it cannot be that we may distinguish memory from imagination somehow in terms of simple ideas.

The memory preserves the original order and position of its ideas.

The imagination transposes and changes these ideas of the memory at its own pleasure.

So it might seem that we could take the original order of the impressions as they were recorded in the memory, and compare them with the rearranged order that they obtained in the imagination. [But try for yourself: recall the series of impressions you had, and then compare that series to how your imagination rearranged them. The complex ideas seem impossible to order into a linear series. And the impressions are so many and so elusive that they are quite difficult to recall in their full entirety and clarity. Hence] Hume says, however, that our minds are not able to do this. So we can neither distinguish the memory and imagination by simple nor by complex ideas.

Recall that in §13 Hume claimed that the only difference there is between ideas and impressions is that impressions are more vivid. Similarly, Hume now claims that the imagination's ideas are fainter than the memory's.

A man may indulge his fancy in feigning any past scene of adventures; nor would there be any possibility of distinguishing this from a remembrance of a like kind, were not the ideas of the imagination fainter and more obscure. (85c)

§199/Appendix Insertion A

Total Recall: Instant Vivacity out of Faint Fancy

Hume will now show that there is not a qualitative difference between the ideas of the memory and imagination.

He has us consider a situation that is something like this:

Two young men see a bull fight. The bull impales one fighter.

The young men become adults. Long after its occurrence, one man refers to this event, but the other cannot recall. So the first one describes all the details of the occurrence: the bright red blood on the dusty ocher ground, the crowd's concerned response, the fighter's cries of agony. But finally the first man describes the beautiful young woman who sat beside the other man. When the fighter was impaled, she embraced the young man and hid her face on his shoulder. Instantly the man recalls everything, every detail in all its vivid clarity. Before having this "total recall," the man heard the description of the scene, and conceived the details as faint ideas of his imagination. For they were not yet "real" to him. But after one significant detail was mentioned, all those previously faint ideas in his imagination instantly became vivid ideas of his memory. [Hume's example is less specific]. As Hume writes:

But as soon as the circumstance is mentioned, that touches the memory, the very same ideas now appear in a new light, and have, in a manner, a different feeling from what they had before. Without any other alteration, beside that of the feeling, they become immediately ideas of the memory, and are assented to. (85c)

§200 / Appendix Insertion B

Different Feelings between Remembered and Imagined Ideas Result from their Different Potencies

So the imagination represents all those objects in our memory. But only a difference in feeling distinguishes ideas of each faculty. This difference in feeling is based on the greater strength and liveliness of the memory's ideas.

§201 An Illustration of the Difference between Imagined and Remembered Ideas

To understand the difference of strength between imagined and remembered ideas, we are to consider a painter. He wants to paint a joyful scene. But he is stuck in a fit of melancholy. So he tries his best to imagine ideas that are joyful. But when he imagines them, they are not as vivid as when he experiences them directly or when he recalls them from memory.

So he seeks out a cheerful friend. His companion's lighter spirits help the painter recall happier times. Now he may better capture the joyfulness he wants in his painting.

He also finds that his more recent happy memories are the most vibrant.

We often are uncertain about the older ideas of our memory which have lost their vivacity. In fact, it might even be unclear if really we are imagining these ideas rather than recalling them.

I think, I remember such an event, says one; but am not sure. A long tract of time has almost worn it out of my memory, and leaves me uncertain whether or not it be the pure offspring of my fancy. (85-86)

§202 Vivid Lies and Remembered Falsehoods

So we see that remembered ideas may become so feeble and obscure that they pass for imagined ideas. Likewise, our imagined ideas might acquire so much force and vivacity as to seem like one of memory's ideas. We then come to actually believe these imagined "memories." Just think of expert liars whose elaborate colorful tales come to even convince their own selves of their specious truth.

This is noted in the case of liars; who by the frequent repetition of their lies, come at last to believe and remember them, as realities; custom and habit having in this case, as in many others, the same influence on the mind as nature, and infixing the idea with equal force and vigour. (86b)

§203 Reasoning from Our Instant Beliefs of Sense and Memory

[Some people have seen moon halos. Others have not. They are quite difficult to describe. Let's presume that we heard of them but never saw one. But we figured that they were either not real or not remarkable.

Then one night we see one.

We run back to our homes to tell others about the moon halo. We say there is an enormous ring of light perfectly surrounding the moon. No one believes us. But you drag them out. They have to "see it to believe it."]

We often believe immediately what we see or remember. Hume says that this immediate belief or assent that accompanies the memory and senses "is nothing but the vivacity of those perceptions they present." (86bc) And these remembered and sensed impressions are distinct from any imagined one for only the reason that their vivacity causes us to believe them immediately. These beliefs, then, provide the building blocks for our judgments and reasoning.

'Tis merely the force and liveliness of the perception, which constitutes the first act of the judgment, and lays the foundation of that reasoning, which we build upon it, when we trace the relation of cause and effect. (86d)

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From the original text:

Sect. v. Of the Impressions of the Senses and Memory.
In this kind of reasoning, then, from causation, we employ materials, which are of a mixed and heterogeneous nature, and which, however connected, are yet essentially different from each other. All our arguments concerning causes and effects consist both of an impression of the memory or, senses, and of the idea of that existence, which produces the object of the impression, or is produced by it. Here therefore we have three things to explain, viz. First, The original impression. Secondly, The transition to the idea of the connected cause or effect. Thirdly, The nature and qualities of that idea.
As to those impressions, which arise from the senses, their ultimate cause is, in my opinion, perfectly inexplicable by human reason, and it will always be impossible to decide with certainty, whether they arise immediately from the object, or are produced by the creative power of the mind, or are derived from the author of our being. Nor is such a question any way material to our present purpose. We may draw inferences from the coherence of our perceptions, whether they be true or false; whether they represent nature justly, or be mere illusions of the senses.
When we search for the characteristic, which distinguishes the memory from the imagination, we must immediately perceive, that it cannot lie in the simple ideas it presents to us; since both these faculties borrow their simple ideas from the impressions, and can never go beyond these original perceptions. These faculties are as little distinguished from each other by the arrangement of their complex ideas. For though it be a peculiar property of the memory to preserve the original order and position of its ideas, while the imagination transposes and changes them, as it pleases; yet this difference is not sufficient to distinguish them in their operation, or make us know the one from the other; it being impossible to recal the past impressions, in order to compare them with our present ideas, and see whether their arrangement be exactly similar. Since therefore the memory, is known, neither by the order of its complex ideas, nor the nature of its simple ones; it follows, that the difference betwixt it and the imagination lies in its superior force and vivacity. A man may indulge his fancy in feigning any past scene of adventures; nor would there be any possibility of distinguishing this from a remembrance of a like kind, were not the ideas of the imagination fainter and more obscure.
It frequently happens, that when two men have been engaged in any scene of action, the one shall remember it much better than the other, and shall have all the difficulty in the world to make his companion recollect it. He runs over several circumstances in vain; mentions the time, the place, the company, what was said, what was done on all sides; till at last he hits on some lucky circumstance, that revives the whole, and gives his friend a perfect memory of every thing. Here the person that forgets receives at first all the ideas from the discourse of the other, with the same circumstances of time and place; though he considers them as mere fictions of the imagination. But as soon as the circumstance is mentioned, that touches the memory, the very same ideas now appear in a new light, and have, in a manner, a different feeling from what they had before. Without any other alteration, beside that of the feeling, they become immediately ideas of the memory, and are assented to.
Since, therefore, the imagination can represent all the same objects that the memory can offer to us, and since those faculties are only distinguished by the different feeling of the ideas they present, it may be proper to consider what is the nature of that feeling. And here I believe every one will readily agree with me, that the ideas of the memory are more strong and lively than those of the fancy.
A painter, who intended to represent a passion or emotion of any kind, would endeavour to get a sight of a person actuated by a like emotion, in order to enliven his ideas, and give them a force and vivacity superior to what is found in those, which are mere fictions of the imagination. The more recent this memory is, the clearer is the idea; and when after a long interval he would return to the contemplation of his object, he always finds its idea to be much decayed, if not wholly obliterated. We are frequently in doubt concerning the ideas of the memory, as they become very weak and feeble; and are at a loss to determine whether any image proceeds from the fancy or the memory, when it is not drawn in such lively colours as distinguish that latter faculty. I think, I remember such an event, says one; but am not sure. A long tract of time has almost worn it out of my memory, and leaves me uncertain whether or not it be the pure offspring of my fancy.
And as an idea of the memory, by losing its force and vivacity, may degenerate to such a degree, as to be taken for an idea of the imagination; so on the other hand an idea of the imagination may acquire such a force and vivacity, as to pass for an idea of the memory, and counterfeit its effects on the belief and judgment. This is noted in the case of liars; who by the frequent repetition of their lies, come at last to believe and remember them, as realities; custom and habit having in this case, as in many others, the same influence on the mind as nature, and infixing the idea with equal force and vigour.
Thus it appears, that the belief or assent, which always attends the memory and senses, is nothing but the vivacity of those perceptions they present; and that this alone distinguishes them from the imagination. To believe is in this case to feel an immediate impression of the senses, or a repetition of that impression in the memory. It is merely the force and liveliness of the perception, which constitutes the first act of the judgment, and lays the foundation of that reasoning, which we build upon it, when we trace the relation of cause and effect.