Context

This section returns to the question raised in Section 2, regarding the origin of our idea of a necessary connection. Having been unable there to establish the source of this idea, the author took a roundabout path by investigating the inferences we draw between causes and effects and the belief that such inferences generate. Having completed that task in Section 13, he turns once again to his original question.

Background

Locke

In a footnote to paragraph 5, the author cites the chapter of Locke’s Essay which he referred to as Locke’s “chapter of power.” This is supposed to represent the most general and popular exposition of the idea of power or efficacy.

The mind being every day informed, by the senses, of the alteration of those simple ideas it observes in things without; and taking notice how one comes to an end, and ceases to be, and another begins to exist which was not before; reflecting also on what passes within itself, and observing a constant change of its ideas, sometimes by the impression of outward objects on the senses, and sometimes by the determination of its own choice; and concluding from what it has so constantly observed to have been, that the like changes for the future be made in the same things, by like agents, and by the like ways,—considers in one thing the possibility of having any of its simple ideas changed, and in another the possibility of making that change; and so comes by that idea which we call power. (An Essay Concerning Human Understanding, Book II, Chapter XXI, “Of Power”)

Malebranche

The author refers in paragraph 7 to an argument found in the Elucidations of (or illustrations upon) Nicolas Malebranche’s The Search after Truth. This argument skeptical, citing the differences in opinion among the philosophers about the nature of power as evidence of there being no power to be found in any being other than God.

In addition, when I think about the different opinions of philosophers on the subject, I cannot doubt what I am proposing. For if they clearly saw what the power of creatures is, or what in them truly has this power, they would all agree in their opinion on it. . . . It seems to me that this diversity of views gives us the right to view men aas often talking about things they do not know, and that since the power of creatures is a fiction of the mind of which we naturally have no idea, it is fancy that leads everyone to imagine it. (Elucidations of the Search after Truth, Elucidation 13)

In the main body of The Search after Truth, Malebranche had advanced an argument very much like the author’s own.

We have only two sorts of ideas, ideas of minds and ideas of bodies; and as we should speak only of what we conceive, we should only reason according to these two kinds of ideas. Thus, since the idea we have of al bodies makes us aware that they cannot move themselves, it must be concluded that it is minds which move them. But when we examine our idea of all finite minds, we do not see any necessary connection between their will and the motion of any body whatsoever. On the contrary, we see that there is none and that there can be none. (The Search after Truth, Book Six, Part Two, Chapter Three)

The Treatise

1. Since Section 2, the author had been seeking an explanation for our idea of the philosophical relation between cause and effect. He had analyzed that idea in terms of contiguity, priority, and necessary connection. He then sought for an answer to this question: “What is our idea of necessity, when we say that two objects are necessarily connected together.” Having failed at 1.3.2.12 to discover an impression that gives rise to the idea of a necessary connection, he undertook to investigate a different issue, why it is necessary that every beginning of existence have a cause. He professed the hope that this investigation would turn up something useful for the task of finding the impression giving rise to the idea of cause and effect. Having failed in Section 3 to discover the source of the belief in “the necessity of a cause” in pure reason, he sought it in experience. But rather than investigate directly how experience might give rise to this belief, he decided it best to “sink” this question into the question of how particular impressions (taken as causes) give rise to particular ideas of new beginnings (taken as effects of those causes). That task was completed in Section 13. So now the search again is for the impression that gives rise to the idea of a necessary connection. Such an impression is required by the Copy Principle enunciated in the first section of Part One.
So take two objects which are supposed to stand in the relation of cause and effect. They are always contiguous and successive, but no other relation between them can be perceived. The view of the two objects can be enlarged to include other like objects in like relations of contiguity and succession. The enlargement seems to do nothing but repeat what has been found in the first instance, but in fact there is more. A new impression is produced by the process of repetition, and it is this impression that gives rise to the idea of necessary connection. This is an impression of the determination of the mind by custom to produce a like idea upon frequent repetition. “’Tis this impression, then, or determination, which affords me the idea of necessity.” The author has finally completed the search begun in Section 2 for the impression demanded by the Copy Principle.

2. The author regards this conclusion to follow from the principles he has established. He notes that it might seem to the reader that it is unremarkable, and as such it would be easily forgotten. But the reader had better pay attention, since this conclusion bears on “one of the most sublime questions of philosophy, viz. that concerning the power and efficacy of causes.” Because of the seriousness of the topic, the author proposes to supply the reader with a fuller account of his doctrine and the arguments leading to it. He raises the hope that he will thereby make the principles of his doctrine more forceful and evident.

3. The issue of the “efficacy of causes” has been a matter of extensive disputes among both ancient and modern philosophers. The author suggests that it would have been well of the disputants to have first examined the idea of the efficacy in question. “This is what I find principally wanting [lacking] in their reasonings, and what I shall here endeavour to supply.”

4. What is the idea of efficacy, agency, power, force, energy, necessity, connexion, and productive quality (“all nearly synonymous”)? Philosophers have opted for “vulgar” or common definitions. But the author’s system requires that we begin by seeking the impressions which give rise to the ideas. If the idea is simple, then the impression will be simple, and if the idea is compound, then the impression will be as well. The author will summarize in paragraph 14 the view that his own, “philosophical” account gives the correct application of the expressions in question, while the vulgar definitions are meaningless because they are applied wrongly. Paragraph 15 begins the positive, philosophical account of the use of these terms, while the next nine paragraphs are devoted to discrediting the meaningless adaptations of the vulgar conception given by the philosophers.

5. The most general and popular explanation, due to Locke, is to posit a power such as is capable of producing new situations in matter, in order to explain the changes in motion and variations in bodies that we experience. But there are two points that show that this definition “is more popular than philosophical.” The first is that reason cannot produce an original idea of its own, but can only operate on ideas copied from impressions of sense and reflection. The second is that reason alone cannot force the conclusion that every beginning necessarily has a cause, as was argued in Section 3. The author will not argue the point any further.

6. Since pure reason cannot justify the positing of a “power,” the idea must come from particular instances of the “efficacy” which arise through sensation and reflection. The author restates his Copy Principle, though substituting ‘object’ for ‘impression.’ Then an idea of efficacy must arise from an efficacious object, and moreover, an object in which the efficacy is “plainly discoverable to the mind, and its operations obvious to our consciousness or sensation.” Otherwise, the idea is “impossible and imaginary.” It might be thought that this dilemma can be avoided by the doctrine of innate ideas, but this “has been already refuted, and is now almost universally rejected in the learned world.” So the task is now to find a “natural production” which reveals the operation and efficacy of a cause in a way that is clear and that cannot give rise to error.

7. We have all kinds of explanations (as listed by Malebranche): substantial forms, accidents or qualities, matter and form, form and accidents, virtues and faculties. The diversity of these opinions is “strong presumption” that they are all “without foundation,” as Malebranche had argued. These principles are unintelligible and inexplicable: philosophers would not have had recourse to them if there were an intelligible substitute. The conclusion to be drawn from this is that no one instance can reveal efficacy, and that the philosophers are no better off than the vulgar in trying to produce one. The author recognizes that this is a negative thesis, and so his only recourse is to challenge these philosophers to show him “an instance of a cause, where we discover the power or operating principle.”

8. The failure of attempts to “fix this power” has led to the thesis that it is unknown. The Cartesians [here the author has Malebranche and his followers in mind] claim that matter is inefficacious. If it could produce anything, it would be motion, but it cannot produce motion because its essence is extension, and extension implies only mobility, and not the power to move objects. [Note: Locke would call mobility a “passive power,” but the author is concerned only with what Locke called “active power.”]

9. The impotence of matter led the Cartesians have recourse to the the deity: it is God who is the “prime mover of the universe.” God, on this thesis, created matter and gave it is “original impulse,” continuing to sustain motion through the exercise of his power. This accounts for the motions, configurations, and qualities of matter.

10. But this thesis of divine power can be sustained only on the false presumption of innate ideas. On the true view, the Copy Principle, there must be an idea of a power in some instance of its exercise. We cannot produce such a thing. Since we have no impression of force, we cannot have an idea of a deity exercising force, which would lead to the impious belief that God has no power. To avoid this impiety, we should conclude that the idea of force which is thereby denied of the deity is an inadequate idea of God’s power.

11. Some philosophers deny the Cartesian claim and attribute power to matter, which is a “second cause” (with God being the “first cause”). However, they admit that efficacy must lie in an unknown quality of matter. In that case, by the Copy Principle, there can be no idea of power or efficacy.

12. [This paragraph is taken from a passage in the Appendix which the author wanted to be inserted here.] The missing impression might be sought in a feeling we have of a power in our own mind when we exercise our will and produce thoughts and feelings. The resulting idea of power is then transferred to matter, as the motions of our bodies obey the will. The first objection to this claim is that it explains nothing, because it has “no more discoverable connection with its effects, than any material cause has with its proper effect.” The reason is that we can distinguish between the exertion of the will and the production of an effect, and so whatever follows after the act of will might not have taken place. There is no way to fix the boundary between when the will is productive and when it is not. “We only perceive their constant conjunction; nor can we even reason beyond it.” There is no internal impression of energy. In footnote 30 from the Appendix, we have the author’s defense of the piety of this conclusion. First, the existence of God can be inferred from the order of the universe, and secondly, the will of God is always accompanied by obedience.

13. An idea of power in general would have to come from ideas of particular powers in an object, given the doctrine of abstract ideas discussed in Section 7 of Part One. But this leads us back to the problem of producing a clear case in which efficacy can be found in a single object. The problem is put differently here. From a single idea we cannot tell that it is impossible for anything but the effect to occur, since this would require demonstration. The possibility of a demonstration has already been rejected. The author repeats his challenge from paragraph 7 that anyone objecting to the thesis produce the example. “But till I meet with such-a-one, which I despair of, I cannot forbear concluding, that since we can never distinctly conceive how any particular power can possibly reside in any particular object, we deceive ourselves in imagining we can form any such general idea.”

14. There is no meaning to the vulgar definitions given by the philosophers. The mistake seems to arise from the misapplication of the true meaning of terms like “power” and “efficacy.” The true meaning will be established in the subsequent sections.

15. The tie between two objects cannot be discovered from the simple consideration of one or both. So we do not derive the idea of power from a single instance. If all conjunctions of objects were entirely different from one another, we would never have an idea of cause and effect.

16. The problem with the other views is that they do not give proper place to “the multiplicity of resembling instances.” This is really all that is needed to solve the problem. The idea of power cannot be something new discovered through repetition, due to the Copy Principle. So what repetition must do is either to “discover or produce something new, which is the source of that idea.” We look to the “effects of the mutiplicity” which is an “enlargement” constituting the idea of power. Power can be understood as an effect of the multiplicity.

17. The first consideration here is that repetition does not discover something new in the repeated objects. If it did, we could draw inferences from the first to the second, and it has been proved that we cannot. Or if we could, it would not matter, because inference cannot produce a new idea.

18. The second consideration is that repetition does not produce something new. The two ideas are distinct and thereby separable. “They are entirely divided by time and place; and the one might have existed and communicated motion, tho’ the other never had been in being.”

19. So nothing new in the object is discovered or produced by resemblance, yet it is the source of the new idea. This source will now be revealed.

20. Observation of repetition produces a new impression in the mind. “We immediately feel a determination of the mind to pass from one object to its usual attendant, and to conceive it in a stronger light upon account of that relation.” This is the only effect of resemblance, so the idea of power is derived from it.

21. The foundation of our inference from cause and effect is the transition arising from the accustomed union. And necessary connection of cause and effect is the foundation of our inference. Therefore, the transition arising from the accustomed union is the necessary connection of cause and effect.

22. Since there is no impression of necessity that arises from the senses, it must arise from reflection. The only internal impression that is relevant is “that propensity, which custom produces, to pass from an object to the idea of its usual attendant. This therefore is the essence of necessity.” Necessity exists in the mind, not in objects. The only alternative to the present view that necessity is a determination of thought is that we have no idea of necessity at all.

23. A comparison is made with the necessity lying in the act of the understanding comparing ideas (“which makes two times two equal four”) and that uniting causes and effects. It is not placed in the causes, nor in God, nor in their concurrence, “but belongs entirely to the soul, which considers the union of two or more objects in all past instances. ’Tis here that the real power of causes is plac’d, along with their connexion and necessity.”

24. This is the most violent paradox in the treatise. Though the proof is straightforward and simple, it will be resisted. The author summarizes the argument again. Although the author enthusiastically endorses his own reasoning, he thinks that “with the generality of readers, the baiss of the mind will prevail.”

25. The author tries to explain this “bias” by noting that this is how we treat other qualities of objects, such as their sounds and smells. The mind “spreads itself” on the objects of the senses. It does the same thing with necessity.

26. The author imagines that the solution given here will be thought extravagant and ridiculous. Were there no mind existent, there would be no causes. To make causes depend on thought reverses the order of nature. “To remove [the power] from all causes, and bestow it on a being, that is no ways related to the cause or effect, but by perceiving them, is a gross absurdity, and contrary to the most certain principles of human reason.”

27. The author makes an analogy with the protests of a blind man who is told that the color scarlet is distinct from the sound of a trumpet. We should not use the idea of power to signify something else which we do not know, but rather use it in a way that is intelligible and will not lead us astray. “This is the case, when we transfer the determination of the thought to external objects, and suppose any real intelligible connexion betwixt them; that being a quality, which can only belong to the mind the considers them.”

28. At least contiguity and succession are independent of the mind, as is the fact that like objects are observed to have like relations of contiguity and succession in many instances. But the power of necessity cannot be similarly endowed on mind-independent reality. The author’s present reasoning can be converted into an instance of this “by a subtility, which it will not be difficult to comprehend.” That is, he is applying the account of the mind-dependence of power to what goes on in the mind.

29. When we say that there is a necessary relation between external objects, all we really have an idea of is the determination of the mind to move from the object to the idea of another object. In the mind, we connect impressions and ideas, and say that the idea follows necessarily from the impression. But this can only mean that the mind begins with an idea of the impression and is determined to form an idea of the idea that resulted from the impression (“the idea of the one to that of the other”). “The uniting principle among our internal perceptions is as unintelligible as that among external objects, and is not known to us any other way than by experience.” So just as there is no insight into “the internal structure or operating principle” of the external object, there is no insight into any principle operating in our minds.

30. The author summarizes his position to this point and explains why he had to take such a devious route to get there. Ordinarily, we would begin by defining the relation of cause and effect and then examine how we make the inference from the one to the other. But because “the nature of the relation depends so much on that of the inference,” the author had to make the “seemingly preposterous” reversal in the order of consideration. Now that he has explained the inference from cause to effect, he can give a definition of the causal relation.

31. As was stated in Part I, Section 5, cause and effect can be viewed as a philosophical or natural relation. It is a philosophical relation when it is the result of comparing different ideas, and it is a natural relation when it is a principle associating two ideas. The author gives two definitions. “An object precedent and contiguous to another, and where all the objects resembling the former are plac’d in like relations of precedency and contiguity to those objects, that resemble the latter.” Cause here is defined purely in terms of objects, but the account of causality was given in terms of ideas. So the author proposes a second definition, which makes reference to the role of the mind in setting up the causal relation. “A cause is an object precedent and contiguous to another, and so united with it, that the idea of the one determines the mind to form the idea of the other, and the impression of the one to form a more lively idea of the other.” The author thinks this is the best he can do. What he finds when he observes the way he generates a causal relation is that first there is in a single instance, one object precedes the other in time and is next to it in space, and then there is an enlargement of his view to other instances, where two objects share the same relation. This is due to the influence of constant conjunction which gives rise to custom. The relation of cause and effect “can never be an object of reasoning.” The author now takes his theory to be established.

32. The author shows four corollaries to his definitions of a cause. Corollary 1: All causes are of the same kind. There is no distinction between the four kinds of causes enunciated by Aristotle: formal, efficient, material, final. The only cause is efficient [i.e., the agent that brings about the change.], “for as our idea of efficiency is deriv’d from the constant conjunction of two objects, wherever this is observ’d, the cause is efficient.” There is no distinction between cause and occasion, as enunciated by Malebranche [i.e., God is the true cause of change, and the preceding object is only the occasion on which God exercises causal power]. According to the definition of cause, “if constant conjunction be imply’d in what we call occasion, ’tis a real cause. If not, ’tis no relation at all, and cannot give rise to any argument or reasoning.”

33. Corollary 2: There is only one kind of necessity, not two (physical and moral, the first pertaining to bodies and the second to minds). It is the same determination of the mind that gives the idea of a causal relation in both cases. Take away necessity and you have chance. The author bases this claim on the fact that the mind is determined or not to pass from an object or another. There are degrees of determination of the mind, based on how strong the conjunction is, and so there are degrees of necessity. This holds even in the physical world, where there are different degrees of “constancy and force” in the conjunction and the determination of the mind. So such variation in human behavior does not indicate a different kind of necessity at work (i.e., “moral necessity”).

34. There is also no distinction between power and its exercise.

35. Corollary 3: It was shown earlier (Section 3) that there is no intuitive or demonstrative argument in favor of the “absolute” or “metaphysical” necessity of the principle that every beginning of existence has a cause. The denial of this kind of necessity to that principle is naturally repugnant to us, but it can be understood easily given the definitions of cause just given. If we define it in terms of constant conjunction, it is possible that there be no preceding and contiguous object which resembles the kind of object that has always preceded the beginning of existence. If we define it in terms of a determination of the mind, it is even more clear that there is no metaphysical necessity, since the determination of the mind is something that “is in itself perfectly extraordinary and incomprehensible.” Moreover, we only know of it through experience and observation, so the “necessity” could not be shown by an intuitive or demonstrative argument.

36. Corollary 4: We have no reason to believe an object exists if we cannot form an idea of it. All reasoning concerning existence is causal, and causal reasoning requires ideas which are constantly conjoined. This is pointed out because it bears on the criticisms made in Part 4, Section 3, concerning matter and substance.

The Enquiry

The goal of Section 7 is to fix, if possible the meaning of these terms [power, force, energy, or necessary connexion, and thereby remove part of that obscurity, which is so much complained of in metaphysics. Hume again solicits the impression of which the ideas of power or necessary connection are copies. He presents an argument for the claim that we cannot discover power in a the first appearance of a single object, because we cannot predict in advance what the effect will be, as the source of activity in the universe is concealed from us. This applies as well to the alleged influence of the will on our actions, as the cause of our actions is equally unknown and incomprehensible. Hume goes on the criticize the occasionalism of Malebranche similarly as in the Treatise. He argues in Part 2 that experience of constant conjunction is what enables us to deem one object cause and the other effect. (Here he describes inference from one single experiment, however accurate or certain, to be justly esteemed an unpardonable temerity, whereas he allowed in Section 8 and Section 15 of the Treatise that such an experiment may be sufficient to allow a universal generalization.) Repetition alone is not sufficient for the judgment of a causal relation, and what is required is a connection felt in the mind of the customary transition of the imagination from one object to its usual attendant, which is the impression from which the idea of a connection is copied. The feeling is one of connection, over and above observed conjunction. Finally, he defines a cause similarly to the way he defined it in the Treatise. In a footnote, he adds that the popular usage of the terms at issue shed no light on its meaning.

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