found in the end, that the same answer will serve for both questions.

SECT. IV. Of the Component Parts of our Reasonings
Concerning Cause and Effect.

Tho' the mind in its reasonings from causes or effects carries its view beyond those objects, which it sees or remembers, it must never lose sight of them entirely, nor reason merely upon its own ideas, without some mixture of impressions, or at least of ideas of the memory, which are equivalent to impressions. When we infer effects from causes, we must establish th existence of these causes; which we have only two ways of doing, either by an immediate perception of our memory or senses, or by an inference from other causes; which causes again we must ascertain in the same manner, either by a present impression, or by an inference from their causes, and so on, till we arrive at some object, which we see or remember.' 'Tis impossible for us to carry on our inferences in infinitum; and the only thing, that can stop them, is an impression of the memory or senses, beyond which there is no room for doubt or enquiry.

To give an instance of this, we may chuse any point of history, and consider for what reason we either believe or reject it. Thus we believe that CESAR was kill'd in the senate-house on the ides of March; and that because this fact is establish'd on the unanimous testimony of historians, who agree to assign this precise time and place to that event. Here are certain characters and letters present either to our memory or senses; which characters we likewise remember to have been us'd as the signs of certain ideas; and these ideas were either in the minds of such as were immediately present at that action, and receiv'd the ideas directly from its existence; or they were deriv'd from the testimony of others, and that again from another testimony, by a visible gradation, 'till we arrive at those who were eye-witnesses and spectators of the event. "Tis obvious all this chain of argument or connexion of causes and effects, is at first founded on those characters or letters, which are seen or remember'd, and that without the authority either of the memory or senses our whole reasoning wou'd See Introd, § 284.

TV

be chimerical and without foundation. Every link of the SEC chain wou'd in that case hang upon another; but there wou'd not be any thing fix'd to one end of it, capable of Of the sustaining the whole; and consequently there wou'd be no cen po belief nor evidence. And this actually is the case with all hypothetical arguments, or reasonings upon a supposition; ins there being in them, neither any present impression, nor belief of a real existence.

I need not observe, that 'tis no just objection to the present doctrine, that we can reason upon our past conclusions or principles, without having recourse to those impressions, from which they first arose. For even supposing these impressions shou'd be entirely effac'd from the memory, the conviction they produc'd may still remain; and 'tis equally true, that all reasonings concerning causes and effects are originally deriv'd from some impression; in the same manner, as the assurance of a demonstration proceeds always from a comparison of ideas, tho' it may continue after the comparison is forgot.

SECT. V. Of the Impressions of the Senses and Memory.

A

In this kind of reasoning, then, from causation, we employ materials, which are of a mix'd and heterogeneous nature, and which, however connected, are yet essentially different from each other. All car 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 produc'd 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.1

As to those impressions, which arise from the senses, their ultimate cause is, in my opinion, perfectly inexplicable by human reason, and 'twill always be impossible to decide with certainty, whether they arise immediately from the object, or are produc'd by the creative power of the mind, or are deriv'd 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,

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cause.

effect.

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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
and the memory from the imagination, we must immediately V
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 distinguish'd from
each other by the arrangement of their complex ideas. For
tho' it be a peculiar property of the memory to preserve the
original order and position of its ideas, while the imagi-
nation 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 wou'd 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.1

It frequently happens, that when two men have been engag'd 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; tho' he considers them as mere fictions of the imagination. But as soon as the circumstance is mention'd, 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, 1 [The two following paragraphs were added in the Appendix.-Ed.]

A

they become immediately ideas of the memory, and are assented to.

SECT.
V.

the senses

Since, therefore, the imagination can represent all the of the imsame objects that the memory can offer to us, and since pressions of those faculties are only distinguish'd by the different feeling and of the ideas they present, it may be proper to consider what memory. 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, wou'd 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 wou'd return to the contemplation of his object, he always finds its idea to be much decay'd, 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 tỏ 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

PART

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Of know-
ledge and
probabi-
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any

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repetition of that impression in the memory. '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.

SECT. VI.-Of the Inference from the Impression to the Idea.

"Tis easy to observe, that in tracing this relation, the inference we draw from cause to effect, is not deriv'd merely from a survey of these particular objects, and from such a penetration into their essences as may discover the dependance of the one upon the other. There is no object, which implies the existence of any other if we consider these objects in themselves, and never look beyond the ideas which we form of them. Such an inference wou'd amount to knowledge, and wou'd imply the absolute contradiction and impossibility of conceiving any thing different. But as all distinct ideas are separable, 'tis evident there can be no impossibility of that kind. When we pass from a present impression to the idea of any object, we might possibly have separated the idea from the impression, and have substituted any other idea in its room.

'Tis therefore by EXPERIENCE only, that we can infer the existence of one object from that of another. The nature of experience is this. We remember to have had frequent instances of the existence of one species of objects; and also remember, that the individuals of another species of objects have always attended them, and have existed in a regular order of contiguity and succession with regard to them. Thus we remember, to have seen that species of object we call flame, and to have felt that species of sensation we call heat. We likewise call to mind their constant conjunction in all past instances. Without any farther ceremony, we call the one cause and the other effect, and infer the existence of the one from that of the other.1 In all those instances, from which we learn the conjunction of particular causes and effects, both the causes and effects have been perceiv'd by the senses, and are remember'd: But in all cases, wherein we reason concerning them, there is only one perceiv'd or remember'd, and the other is supply'd in conformity to our past experience.

1 [See Introd. §§ 284 and 311.]