Notes on Hume’s Treatise

by G. J. Mattey

Book 1
Of the UNDERSTANDING
PART 3
Of knowledge and probability.

Sect. 3. Why a cause is always necessary.

Context

Section 2 established that one component of the idea of cause and effect is the idea of the relation of necessary connection between the cause and the effect. However, the author was unable in Section 2 to discover directly any “impression or impressions, from which its idea is deriv’d” (Section 2). This result conflicts with his “firmly established” principle that every idea is a copy of an impression (Section 2). Rather than give up his principle, the author decides to abandon at this point “the direct survey of this question of that necessary connexion, which enters into the idea of cause and effect, and endeavour to find some other questions, the examination of which will afford a hint, that may serve to clear up the present difficulty.” The first question, addressed in this section, is, “For what reason we pronounce it necessary, that every thing whose existence has a beginning, shou’d also have a cause?” This approach is indirect because it considers the relation of necessary connection in the context of its use in a philosophical principle. The principle contains the notion of a beginning of existence, which had not appeared in the initial discussion in Section 2 of the relation of a necessary connection or of causality itself. In the discussion of the relation of cause and effect, the author had been using examples of the effect of one object upon another, or what in the present section, paragraph 3, is called “a new modification of existence.” Here “beginning of existence” is allowed to include new modifications of existing things as well as “every new existence” (paragraph 3).

Background

In the works of the author’s predecessors, the main motivation for demonstrating the principle that everything whose existence has a beginning must have a cause was religious. The principle was used as the basis of a causal argument for the existence of God. The author mentions three arguments for the principle by modern philosophers.

Hobbes

In Thomas Hobbes’s 1651 Leviathan, the following causal argument for God’ existence is given. It occurs in the context of a discussion concerning the origin of religion in human beings. One of the qualities “peculiar to the nature of Man” is that “upon the sight of any thing that hath a Beginning, to think also it had a cause, which determined the same to begin, then when it did, rather than sooner or later" (Part I, Chapter 12). This principle is then put to use.

But the acknowledging of one God Eternall, Infinite, and Omnipotent, may more easily be derived, from the desire men have to know the causes of naturall bodies, and their severall vertues, and operations; than from the feare of what was to befall them in time to come. For he that from any effect hee seeth come to passe, should reason to the next and immediate cause thereof, and from thence to the cause of that cause, and plonge himself profoundly in the pursuit of causes; shall at last come to this, that there must be (as even the Heathen Philosophers confessed) one First Mover; that is, a First and Eternall cause of all things; which is that which men mean by the name of God . . . . (Part I, Chapter 12)
In the 1654 Of Liberty and Necessity, we find an argument for the claim that one should reason from effect to cause.
Also the sixth Point,—that a man cannot imagine any thing to begin without a Cause,—can no other way be made known, but by trying how he can imagine it; but if he try, he shall find as much reason (if there be no Cause of the thing) to conceive it should begin at one time as another; that is, he hath equal reason to think it should begin at all times; which is impossible: and therefore he must think there was some special Cause why it began then, rather than sooner or later; or else, that it began never, but was Eternal. (From the 1812 edition, edited by Philip Mallet, page 159.)
In 1656 there was published Elements of Philosophy, the First Section Concerning Body, a translation of Elementa Philosophiae Sectio prima de Corpore of 1655. The first selection is from Chapter VIII.

19. Whatsoever is at Rest, will alwayes be at Rest, unless there be some other Body besides it, which by endeavouring to get into its Place by motion, suffers it no longer to remain at Rest. For suppose that some Finite Body exist, and be at Rest, and that all Space besides be Empty; if now this Body begin to be Moved, it will certainly be Moved some way; Seeing therefore there was nothing in that Body which did not dispose it to Rest, the reason why it is Moved this way is in something out of it; and in like manner, if it had been Moved any other way, the reason of Motion that way had also been in something out of it; but seeing it was supposed that Nothing is out of it, the reason of its Motion one way would be the same with the reason of its Motion every other way; wherefore it would be Moved alike all ways at once; which is impossible.

In like manner, Whatsoever is Moved, will alwayes be Moved, except there be some other Body besides it, which causeth it to Rest. For if we suppose Nothing to be without it, there will be no reason why it should Rest now, rather then at another time; wherefore its Motion would cease in every particle of time alike; which is not intelligible.

The second selection is from Chapter IX.
8. But if a Body work upon another Body at one time, and afterwards the same Body work upon the same Body at another time so, that both the Agent and Patient, and all their parts, be in all things as they were; and there be no difference except onely in time, that is, that one Action be former, the other later in time; it is manifest of it self, that the Effects will be Equal and Like; as not differing in any thing besides time. And as Effects themselves proceed from their Causes; so the diversity of them depends upon the diversity of their Causes also.

Locke

In the 1689 An Essay concerning Human Understanding, John Locke also gave a causal argument for the existence of God. His first premise is that something actually exists, since he himself exists. The following contains the causal principle as the second premise and the argument itself.

Man knows, by an intuitive certainty, that bare nothing can no more produce any real being, than it can be equal to two right angles. If a man knows not that nonentity, or the absence of all being, cannot be equal to two right angles, it is impossible he should know any demonstration in Euclid. If, therefore, we know there is some real being, and that nonentity cannot produce any real being, it is an evident demonstration, that from eternity there has been something; since what was not from eternity had a beginning; and what had a beginning must be produced by something else. (Book IV, Chapter 10, Section 3)
In his first letter to Bishop Stillingfleet of Worcester (1686/7), Locke elaborated on his appeal to the principle.
But “every thing that has a beginning must have a cause,” is a true principle of reason, or a proposition certainly true; which we come to know by the same way, i.e. by contemplating our ideas, and perceiving that the idea of beginning to be, is necessarily connected with the idea of some operation; and the idea of operation, with the idea of something operating, which we call a cause; and so the beginning to be, is perceived to agree with the idea of a cause, as is expressed in the proposition: and thus it comes to be a certain proposition; and so may be called a principle of reason, as every true proposition is to him that perceives the certainty of it. (Locke Works, Volume 3, p. 62)

Clarke

Samuel Clarke’s 1705 A Demonstration of the Being and Attributes of God draws the same conclusion as did Locke, that something has existed from eternity, on roughly the same basis.
For since Something Now Is; ’tis manifest that Something always Was: Otherwise the Things that Now Are, must have risen out of Nothing, absolutely and without Cause: Which is a flat Contradiction in Terms: for to say a Thing is produced, and yet that there is no Cause at all of that Production, is to say that Something is Effected when it is Effected by Nothing, that is, at the same time when it is not Effected at all. Whatever Exists, has a Cause of its Existence, either in the Necessity of its own Nature; and then it must have been Eternal: Or in the Will of some other Being; and then that Other Being must, at least in the Order of Nature and Causality, have Existed before it. (Proposition I, pp. 18-19)

The Treatise

1. The author observes that “’Tis a general maxim in philosophy, that whatever begins to exist, must have a cause of existence.” We use this maxim or principle in our reasoning without proof of its truth, as it is taken to be known intuitively. However, given the account of intuitive knowledge in Section 2, the author claims that there is in fact “no mark of any such intuitive certainty.” On the contrary, “’tis of a nature quite foreign to that species of conviction.”

2. It is claimed in Section 2 that certainty is confined to comparisons of ideas present to the mind, as well as the mind’s ”discovery” that if there is no change in the relata (objects being related), then there can be no change in the relation itself. The author had found there to be four such relations that can be known intuitively. (See Section 1 for the four relations admitting of such comparison.) None of these is “imply’d in” the general causal maxim, so there is no basis in them of the causal relation. For example, resembling things continue to resemble each other so long as they do not undergo any change. But one surely cannot derive the relation of cause and effect from that of resemblance. The author challenges anyone who thinks that the relation of cause and effect is intuitive to find some other “infallible” relation such as resemblance to be implied by the causal principle.

3. The author now offers another argument to prove not only that the principle is not intuitively certain, but that it is not demonstratively certain either. If it can be demonstrated that a cause is required for every new existence or change in what does exist, then it is impossible for the the thing to exist (or change) without a cause. So if it is possible for something to exist without a cause, then there is no demonstration of the principle. The author first notes that the idea of the cause and the idea of the effect are distinct ideas, for “’twill be easy for us to conceive any object to be non-existent this moment, and existent at the next, without conjoining to it the distinct idea of a cause or productive principle.” He then appeals to his general principle that what is distinct is separable in the imagination. So, the ideas of cause and effect are separable in the imagination. But if the ideas are separable in the imagination, then it is at least possible that they are separable in reality, and if it is possible that they are separable in reality, it is not impossible for something to exist or change without a cause, in which case there is no demonstration that a cause is necessary for any beginning of existence.

4. The author concludes that if there can be no demonstration of the principle, then all extant attempts at demonstration are fallacious in some way or other. He considers three arguments purporting to establish the principle, beginning with one he attributes to Hobbes. If an object begins to exist, then there must be something to “fix” its beginning to exist, because if there were not, “it must remain in eternal suspence, and the object can never begin to be, for want of something to fix the beginning.” The beginning cannot be fixed by space or time, as all positions in them are “in themselves equal,” and so there is nothing to determine that the beginning occurs in one place at one time rather than in some other place or time. So, there must be something else, the cause, which fixes the beginning. The author rebuts this argument in a somewhat roundabout way. First, note that the alleged possibility of an object’s beginning to exist without a cause is not taken to be absurd in itself, but rather requires a demonstration. The premise of the demonstration is that it is absurd that the object could exist where and when it does unless there is a cause. So the absurdity of the object’s beginning to exist without something to fix its time or place is taken for granted, while the absurdity of its not having a cause one requires a proof. Second, we could reverse the argument and claim that because it is absurd that an object begins to exist without a cause, it is absurd that an object exists when and where it does. Therefore, the author concludes, the two arguments are “both upon the same footing.” The absurdity of either one is the basis of the absurdity of the other, and so the two arguments “must stand or fall by the same reasoning.” So, the premise of Hobbes’s argument, that it is absurd for a thing to begin to exist without something to fix its beginning in a determinate time and place, is just as much in need of a demonstration as the conclusion that it was supposed to demonstrate, that it is absurd for a thing to exist without a cause.

5. The second argument is attributed to Clarke, and it is said to labor “under an equal difficulty,” whose similarity to the difficulty with the first argument is not immediately apparent, but which will be explained in the comments below on paragraph 7. The argument is by reductio ad absurdum. If a thing begins to exist without a cause, then it would be the cause of itself. But if it is the cause of itself, it existed before it existed, which is an impossibility. So, no thing begins to exist without a cause. While the author grants the premise that nothing is a cause of itself, he notes that the first premise begs the question. It assumes that the thing has a cause of its existence, denying only that the cause is something else. “But to say that anything is produc’d, or to express myself more properly, comes into existence, without a cause, is not to affirm, that ’tis itself its own cause; but on the contrary in excluding all external causes, excludes a fortiori the thing itself, which is created.” The question-begging move is to suppose “that upon the exclusion of one productive principle, we must still have recourse to another,” which presupposes that “’tis utterly impossible any thing can ever begin to exist without a cause.”

6. Locke is said to be the source of the third argument. If a thing begins to exist without a cause, then nothing is its cause. However, nothing cannot be a cause, any more than it can be equal to two right angles. From this it follows that no thing begins to exist without a cause, or that “every object has a real cause of its existence.”

7. The author takes this argument to be very weak and subject to the same criticism as the argument attributed to Clarke. Where as Clarke concluded, from the assumption that a thing has no cause of its beginning, that it must cause itself, Locke concluded that it must have nothing as a cause. But whether it has a cause at all is “the very point in question,” and if the reductio assumption is not to beg the question, it must exclude all causes. Note that the author charges that all three arguments are infected with this fallacy. The question-begging character of the second and third arguments is clear, but the author did not bring it up in his criticism of the first argument. The problem there is that the assumption that a thing begins to exist without a cause must exclude all causes of its beginning to exist, including the cause of its beginning to exist at the time and place it does.

8. As if these question-begging arguments are not bad enough, there is another argument whose adopters are “still more frivolous” than the three authors criticized above. The argument is that the idea of an effect implies the idea of a cause, since “effect” is a relative term. “But this does not prove, that every being must be preceded by a cause; no more than it follows, because every husband must have a wife, that therefore every man must be marry’d.” The question is not whether every effect has a cause, but whether every object that begins to exist has a cause. “And this I assert neither to be intuitively nor demonstrably certain, and hope to have prov’d it sufficiently by the foregoing arguments.”

9. The only remaining source of the opinion that every beginning of existence must have a cause is “observation and experience.” But how could a principle of this sort arise from experience? The author decides that it will be more convenient to “sink” this question in the second question posed in Section 2: “Why we conclude, that such particular causes must necessarily have such particular effects, and why we form an inference from one to the another?” He will press on to try to answer this question, of which he conjectures hopefully that the answer to the second question (given in Section 6) will serve to answer the first (as indeed occurs in Section 14).

The Enquiry

In the Enquiry, the author does not consider the general proposition that every beginning of existence has a cause. Instead, in Section 4 he focuses exclusively on the second question noted just above, why particular causes have particular effects, and how the inference from the one to the other arises.

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