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we have done so, 'tis in vain to pretend to reasoning SECT. and philosophy.

knowledge.

Of

SECTION II.

OF PROBABILITY, AND OF THE IDEA OF CAUSE AND

EFFECT.

V

This is all I think necessary to observe concerning those four relations, which are the foundation of science; but as to the other three, which depend not upon the idea, and may be absent or present even while that remains the same, 'twill be proper to explain them more particularly. These three relations are identity, the situations in time and place, and causation.

All kinds of reasoning consist in nothing but a comparison, and a discovery of those relations, either constant or inconstant, which two or more objects bear to each other. This comparison we may make, either when both the objects are present to the senses, or when neither of them is present, or when only one. When both the objects are present to the senses along with the relation, we call this perception rather than reasoning; nor is there in this case any exercise of the thought, or any action, properly speaking, but a mere passive admission of the impressions through the organs of sensation. According to this way of thinking, we ought not to receive as reasoning any of the observations we may make concerning identity, and the relations of time and places since in none of them the mind can go beyond what is immediately present to the senses, either to discover the real exist

Of

and

PART ence or the relations of objects. 'Tis only causation,

which produces such a connexion, as to give us as

surance from the existence or action of one object, knowledge

that 'twas followed or preceded by any other existence probability,

or action; nor can the other two relations ever be made use of in reasoning, except so far as they either affect or are affected by it. There is nothing in any objects to persuade us, that they are either always remote or always contiguous ; and when from experience and observation 2 discover, that their relation in this particular is invariable, we always conclude there is some secret cause which separates or unites them. The same reasoning extends to identity. We readily suppose an object may continue individually the same, though several times absent from and present to the senses; and ascribe to it an identity, notwithstanding the interruption of the perception, whenever we conclude, that if we had kept our eye or hand constantly upon it, it would have conveyed an invariable and uninterrupted perception, But this conclusion beyond the impressions of our senses can be founded only on the connexion of cause and effect ; nor can we otherwise have any security that the object is not changed upon us, however much the new object may resemble that which was formerly present to the senses. Whenever we discover such a perfect resemblance, we consider whether it be common in that species of objects; whether possibly or probably any cause could operate in producing the change and resemblance; and according as we deter, mine concerning these causes and effects, we form our judgment concerning the identity of the object.

Here then it appears, that of those three relations, which depend not upon the mere ideas, the only one that can be traced beyond our senses, and informs us

II.

Of

and of

cause and

of existences and objects, which we do not see or feels $ECT. is causation. This relation therefore we shall endeavour to explain fully before we leave the subject of the

probability, understanding

the idea of To begin regularly, we must consider the idea of causation, and see from what origin it is derived. "Tis

effect. impossible to reason justly, without understanding perfectly the idea concerning which we reason; and 'tis impossible perfectly to understand any idea, without tracing it up to its origin, and examining that primary impression, from which it arises. The examination of the impression bestows a clearness on the idea ; and the examination of the idea bestows a like clearness on all our reasoning

Let us therefore cast our eye on any two objects, which we call cause and effect, and turn them on all sides, in order to find that impression, which produces an idea of such prodigious consequence. At first sight Į perceive, that I must not search for it in any of the particular qualities of the objects; since, whichever of these qualities I pitch on, I find some object that is not possessed of it, and yet falls under the denomination of cause or effect. And indeed there is nothing existent, either externally or internally, which is not to be considered either as a cause or an effect; though 'tis plain there is no one quality which universally belongs to all beings, and gives them a title to that de nomination.

The idea then of causation must be derived from some relation among objects; and that relation we must now endeavour to discover. I find in the first place, that whatever objects are considered as causes or effects, are contiguous; and that nothing can operate in a time or place, which is ever so little removed

and

PART from those of its existence. Though distant objects Ill.

may sometimes seem productive of each other, they Of

are commonly found upon examination to be linked knowledge

by a chain of causes, which are contiguous among probability.

themselves, and to the distant objects; and when in any particular instance we cannot discover this connexion, we still presume it to exist. We may therefore consider the relation of contiguity as essential to that of causation; at least may suppose it such, according to the general opinion, till we can find a more proper occasion * to clear up this matter, by examining what objects are or are not susceptible of juxtaposition and conjunction.

The second relation I shall observe as essential to causes and effects, is not so universally acknowledged, but is liable to some controversy. 'Tis that of priority of time in the cause before the effect. Some pretend that 'tis not absolutely necessary a cause should precede its effect; but that any object or action, in the very first moment of its existence, may exert its productive quality, and give rise to another object or action, perfectly cotemporary with itself. But beside that experience in most instances seems to contradict this opinion, we may establish the relation of priority by a kind of inference or reasoning. 'Tis an established maxim both in natural and moral philosophy, that an object, which exists for any time in its full perfection without producing another, is not its sole cause; but is assisted by some other principle which pushes it from its state of inactivity, and makes it exert that energy, of which it was secretly possessed. Now if any cause may be perfectly cotemporary with its effect, 'tis certain, according to this maxim, that they must

• Part IV. Sect. 5.

11.

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all of them be so; since any one of them, which re- ŞECT. tards its operation for a single moment, exerts not itself at that very individual time, in which it might

probability, have operated; and therefore is no proper cause.

The and of

the idea of consequence of this would be no less than the destruc

cause and tion of that succession of causes, which we observe in

effect. the world; and indeed the utter annihilation of time. For if one cause were cotemporary with its effect, and this effect with its effect, and so on, 'tis plain there would be no such thing as succession, and all objects must be co-existent.

If this argument appear satisfactory, 'tis well. If not, I beg the reader to allow me the same liberty, which I have used in the preceding case, of supposing it such. For he shall find, that the affair is of no great importance.

Having thus discovered or supposed the two relations of contiguity and succession to be essential to causes and effects, I find I am stopped short, and can proceed no farther in considering any single instance of cause and effect. Motion in one body is regarded upon impulse as the cause of motion in another. When we consider these objects with the utmost attention, we find only that the one body approaches the other; and that the motion of it precedes that of the other, but without any sensible interval. 'Tis in vain to rack ourselves with farther thought and reflection upon this subject. We can go no farther in considering this particular instance.

Should any one leave this instance, and pretend to define a cause, by saying it is something productive of another, 'tis evident he would say nothing. For what does he mean by production? Can he give any definition of it, that will not be the same with that of cau

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