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Philosophy of Mind

David Hume’s Treatment of Mind

Aaron Preston
University of Southern California

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ABSTRACT: This paper critically examines Hume’s argument against the knowledge/existence of substantival mind. This denial is rooted in his epistemology which includes a theory of how complex ideas which lack corresponding impressions are manufactured by the imagination, in conjunction with the memory, on the basis of three relations among impressions: resemblance, continuity and constant conjunction. The crux of my critique consists in pointing out that these relations are such that only an enduring, unified agent could interact with them in the way Hume describes. I note that Hume attempts to provide such an agent by invoking the activities of imagination and memory, but that it is unclear where these belong in his system. After discussing the relevant possibilities, I conclude that there is no category within the limits of his system that can accommodate the faculties and allow them to do the work Hume assigned to them. I then note that Hume’s rejection of substantival mind rests upon the assumption that something like substantival mind exists; for the action of the latter is required for the proper functioning of the process of fabrication which creates the fictitious notion of substantival mind. My concluding argument is that if the existence of substantival mind is implicit in Hume’s argument against substantival mind, then his argument resembles an indirect proof, and ought to be considered as evidence for, rather than against, the existence of substantival mind.

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It is well known that David Hume rejected any idea of a 'substance of the mind' that would account for, among other things, personal identity. I will attempt to show that Hume's argument against the existence of substantival mind presupposes that such an entity actually exists, and that therefore his argument can be interpreted as an indirect proof for the existence of substantival mind; that is, as a reductio ad absurdum of his own position. To demonstrate this, I will give first a brief rehearsal of Hume’s epistemology in general, then as it is applied specifically to the mind.

Hume’s Epistemology

The great project of Empiricism, in its incipience, was to discover, in Locke's words, "...the original, certainty, and extent of human knowledge..." (1) In his Treatise of Human Nature, Hume is intent upon developing a "science of Man" (2) which would acquaint us with "the extent and force of human understanding, and [which] could explain the nature of the ideas we employ, and of the operations we perform in our reasonings." (3) Hume hoped that this 'Science of Man' would serve as a solid foundation for all other sciences, both natural and philosophical, and that it would ultimately eradicate conflicting theories in all fields by defining the limits of human knowledge.

For Hume, all knowledge originates with experience, and all experience is of one’s own perceptions. We have direct knowledge only of perceptions, not of what the perceptions are of (if, indeed, they may be counted as of anything); for the perception stands between the perceiving mind and its supposed real-world object. Hume says,

...'tis impossible for us so much as to conceive or form an idea of any thing specifically different from [our perceptions]. Let us fix our attention out of ourselves as much as possible: Let us chase our imaginations to the heavens, or to the utmost limits of the universe; we never really advance a step beyond ourselves, nor can conceive any kind of existence, but those perceptions, which have appeared in that narrow compass. (4)

Hume recognizes two kinds of perceptions: impressions and ideas. The distinguishing factor between these is simply the degree of "force and liveliness with which they strike upon the mind". (5) Impressions enter the mind with "force and violence", while ideas are but the "faint images" of these which occur in thought and reasoning. (6) Further, all perceptions, both impressions and ideas, can be either simple or complex. Simple perceptions are "such as admit of no distinction nor separation", while complex perceptions "are contrary to these and may be distinguished into parts". (7) Hume observes that, while all of his simple ideas have exactly corresponding impressions, many of his complex ideas do not; and that, furthermore, many of his complex impressions are not represented exactly with complex ideas. He gives the example of his idea of the New Jerusalem from the New Testament book of Revelation, with its streets of gold and walls made of gems — a complex idea for which he has no exactly corresponding complex impression; and conversely, his idea of Paris, which though indeed complex does not exactly represent his impression of that city. (8) Upon this note Hume establishes the principle "That all our simple ideas in their first appearance are derived from simple impressions, which are correspondent to them, and which they exactly represent." (9) But this is not true for complex ideas, for some are 'non-corresponding'. This treatment of perceptions allows for a very 'reasonable' scepticism toward the existence of those things supposed to be represented by non-corresponding complex ideas.

Of course, applied rigorously Hume’s system can substantiate neither a firm denial nor an affirmation of the existence of these things — it is an epistemology, not an ontology. However, the tendency, not only of Hume himself, but of those who have since accepted his work, has been to act as though this epistemology had genuine ontological implications. It is only in assuming that the would-be objects of non-corresponding complex ideas positively do not exist that it becomes necessary to propose an explanation for the existence of those ideas. That is, if Hume did not grant his epistemology ontological consequence, there would be no need to progress beyond scepticism. That he feels the need to offer an explanation for the existence of these non-corresponding complex ideas belies the fact that he from the beginning assumes the possibility that they do not originate in the 'external world'. Thus, out of the scepticism emerges the now familiar scheme of psychological manufacture. The imagination, Hume claims, combines otherwise legitimate simple ideas, creating from them complex ideas of whatever form it likes; thus generating, by these fabricative acts, the 'objects' of our illusory experience. But, it seems unlikely that such random fabrications of the imagination should follow so regular a pattern that they could become the objects of our seemingly well-ordered experience. Hume insists, therefore, that there must be some 'principles of association' which guide the imagination’s activities in this vein. He says,

Were ideas entirely loose and unconnected, chance alone would join them; and 'tis impossible that the same simple ideas should fall regularly into complex ones...without some bond of union among them. (10)

This bond of union, these principles of association, Hume decides, are three: Resemblance, Spatial and Temporal Contiguity, and Cause-Effect. Resemblance is easily understood. Impressions may share common properties. This results in resemblance not only between the impressions themselves, but between the ideas which correspond to those impressions. This resemblance then facilitates the conveyance of the mind from one idea to another. Spatial and Temporal Contiguity are likewise fairly straightforward. Hume explains that the senses must take their objects as they are found, contiguous to one another; and that the imagination "must by long custom acquire the same manner of thinking". (11)

Hume encounters a problem in the relation of cause and effect. Causation is the only one of the three principles of association which might allow an inference to something beyond sensory data. Hume, though, denies this possibility, saying:

There is nothing in any objects to persuade us, that they are either always remote or always contiguous; and when from experience and observation we discover, that their relation in this particular is invariable, we always conclude that there is some secret cause, which unites or separates them. (12)

There is no rational justification for belief in causation, for there is no "impression which produces an idea of such prodigious consequence." (13) Ultimately, causation is reduced to, in Hume’s words, "constant conjunction" — the presence of impressions which, by chance, always go together. (14)

Hume’s Treatment of Mind

But what is this imagining and associating element which Hume blames for the manufacture of our notion of causation and of other 'non-corresponding' complex ideas? Usually, such activities would be explained in terms of the faculties of a mind; but Hume does not allow for such an entity. According to Hume, the mind belongs alongside the ideas it purportedly creates, in the realm of fiction. He challenges:

I desire those philosophers, who pretend that we have an idea of the substance of our minds, to point out the impression that produces it, and tell distinctly after what manner that impression operates, and from what object it is derived. (15)

Again we enter the arena of epistemological deconstruction, only this time with the mind as our 'object'. The process is the same as with cause and effect: we have no simple idea of the mind, nor of the substance of the mind — all we have are the simple impressions and ideas of sensations. Each of these impressions and ideas are distinct, thus separable, from any others, including the fictitious idea of mind. Hume says:

since all our perceptions are different from each other, and from everything else in the universe, they are also distinct and separable, and may be considered as separately existent, and may exist separately, and have no need of anything else to support their existence. (16)

Not only is there no idea of mind as a substance, but neither is there any need for it, since perceptions can exist in themselves. Granting this epistemological paradigm ontological consequence, as Hume seems to do, all that is left of 'the mind' are these individual perceptions. The result is the well-known 'bundle theory' of personal identity. In Hume's own words, a person may be regarded as "nothing but a bundle or collection of different perceptions, which succeed each other with an inconceivable rapidity, and are in a perpetual flux and movement". (17)

Hume realises that this account of the mind (and, really, of the person) creates a special problem for our idea of personal identity. Whence comes the notion that a stream of independent perceptions forms one enduring entity? Really, this question is applicable to all experience. If, as Hume seems to say, experience consists in distinct and separable simple perceptions, how can any fictitious complex idea be formed, whether of the self or of an other? To construct such a fiction will require more than the imagination. If there is never more than one simple perception present at a time, the imagination will need to make use of perceptions not currently present in order to form complex fictions. That is, it will have to somehow remember past perceptions in order to combine them with whatever perception is now present. But remembering is not a power proper to the imagination — it is a faculty unto itself. Recognising this, Hume invokes what seems to be a distinct faculty: the memory. Hume says:

As the memory alone acquaints us with the continuance and extent of this succession of perceptions, 'tis to be considered, upon that account chiefly, as the source of personal identity. Had we no memory, we should never have any notion of causation, nor consequently of that chain of causes and effects which constitute our self or person. But having once acquired this notion of causation from the memory, we can extend the same chain of causes, and consequently the identity of our persons, beyond our memory, and can comprehend times and circumstances and actions which we have entirely forgot, but suppose in general to have existed. (18)

The latter part of this statement — i.e., the extending and the comprehending — seems to refer the action of the imagination. The fabrication of complex fictions, therefore, involves the interaction of the imagination and the memory.

That is Hume’s epistemology. In a nutshell: many of the notions of things which we often take to be given in our experience, e.g., substance, personal identity, and other causal relations, are fictions which the imagination and memory are jointly encouraged to produce in reaction to three phenomena among impressions: resemblance, spatial and temporal contiguity, and constant conjunction. Because things appear to be similar, seem to be uninterrupted, and are usually found in the same combinations and orders, "we often feign some new and unintelligible principle that connects objects together, and prevents their interruption and variation". (19)

The Need for Something Beyond

Having run quickly through the complexities of the Humean epistemology, I will now discuss some issues which stand open to criticism. First, it is clear that the whole scheme of psychological fabrication requires an agent. Hume attempts to provide an agent in the form of the 'faculties' of imagination, memory, and so-forth. Moreover, though, it is apparent that this agent must be enduring and unified. This is simply to say that there must be something which is capable of being aware of, being influenced by, and acting upon the principles of association; and those principles seem to be such that only a continuing observer could be made aware of them, and that only a unified observer could be moved to use them to construct fictions in the way Hume describes.

First, the agent must endure through time. Hume seems to recognise this when he insists that the imagination "must by long custom acquire the same manner of thinking", (20) i.e., in order for the imagination to create a fiction, it must have repeated experiences of objects which resemble, are contiguous, and are constantly conjoined. But in order to have repeated experiences it would seem that the agent must endure through time. Moreover, it is precisely Hume's recognition of this need that occasions his invocation of memory in his discussion of personal identity. Memory, he says, acquaints us with the continuance of the stream of perceptions. In order to do this, it would seem that the memory itself must continue right along with that stream while in some sense standing apart from it. Second, because there are multiple faculties involved in the process of fabrication (imagination and memory), there must be some principle of unity which joins them together; for the imagination and the memory must somehow form a unit so that the imagination has unhindered access to the repository of simple ideas in the memory, and the memory in turn must have uninterrupted access to the fabrications of the imagination. In the end, however, the system does not allow for a continuing, unified observer. All that it allows are distinct and separable simple perceptions which exist independently.

Of course, it seems that Hume intends that the faculties should somehow solve these problems, though it is unlikely that he really meant these to form an enduring, unified agent. But, if he did not, they do not solve the problems. We may ask where, in this world of separate atomic structures, are the faculties to be located? Normally we would think of faculties as faculties of a mind, or perhaps of a person; but these are not real things for Hume. They are fictions. The mind and the person fade away into a series, or a collection of perceptions; and there is no place amidst these perceptions for the inherence of enduring faculties such as imagination or memory. The mind itself, being only a moment-by-moment succession of individual impressions, seems incapable of doing the sort of remembering and associating necessary to make any use of Resemblance, Contiguity, or Constant Conjunction.

The faculties, whatever they are, are not constituents of the Humean mind, for they are neither ideas nor impressions. Or are they? What nature does Hume mean to give the faculties by introducing them into his system? Does he mean to treat them as 'things-in-themselves', or only as perceptions, possibly of things? On the one hand, it seems that the most one might claim within the limits of Humean epistemology are impressions or ideas of these faculties, or perhaps of the acts of these faculties. But perceptions of the faculties will not create the enduring, unified agent Hume needs. A fleeting perception, or a series of them, simply does not seem to be the sort of thing which could acquire a habit, or custom; but there is nothing else present to do so. Also, we must ask whether our ideas of these are simple or complex, and whether they have corresponding impressions or not. If they are complex and 'non-corresponding', can they possibly avoid sharing the fate of the ideas of mind, and of cause and effect, viz., epistemological deconstruction? And if they are of the 'corresponding' variety, simple or complex, they still fail to provide a unified agent; for one cannot provide unity among a set of distinct and separable perceptions simply by adding more distinct and separable perceptions. Our perceptions of memory and imagination — and these seems to be all that Hume’s epistemology will allow — , therefore contribute nothing to a solution of this problem.

On the other hand, neither will venturing beyond the limits of this epistemology (as Hume seems to do) to invoke these faculties in themselves grant a solution. When Hume invokes memory to account for unity among the perceptions, he comes close to begging the question, for it seems he must assume the existence of some unknown unifying principle among the faculties themselves, which enables the memory, as one of those faculties, to explain the unity of the perceptions. Ultimately, he succeeds only in removing the problem of unity one step, from the perceptions to the faculties.

In the end, there seems to be no category within the limits of the Humean epistemology to which these faculties might belong and, at the same time, do the work Hume needs them to do. As perceptions, they fail to provide an adequate agent, while, as 'things-in-themselves' they not only violate the limits of Hume’s own epistemology, but result in a question-begging, ad hoc type of solution; which is, of course, no solution at all. Humean Empiricism, therefore, requires something beyond mere sense experiences (perceptions) which is capable of unifying experience —   something to which perceptions might in some way belong. At the very least, it requires something which enables a consistent explanation of the 'common-sense' or 'nave' view of experience, even if that view be delusion; but the Humean view is incapable of providing it. In order to account for this 'common-sense' view, Hume must subtly invoke the enduring, unified faculties of imagination and memory, which are, on his own account, faculties of nothing — not of a mind, certainly not of perceptions.

The whole of Hume’s 'delusional epistemology' requires the existence of and knowledge of an enduring, unified agent with faculties of imagination and memory, yet his metaphysical schema does not explain how this entity is either ontologically possible or epistemologically admissible. In fact, it strongly suggests that such an entity is neither. This, I believe, poses a serious problem for Humean Empiricism, for it cannot, on its own grounds, account for the elements which alone would make it possible. By attempting to reduce experience to 'sense perception', Empiricism eliminates the elements which make sense perception possible. One historian of philosophy has noted,

The attempt to by-pass or exclude metaphysics will often be found to involve a concealed metaphysical assumption, an unavowed theory of being. In other words, the theory that scientific advance pushes metaphysics out of the picture is mistaken. Metaphysics simply reappears in the form of concealed assumptions. (21)

Hume’s 'concealed assumption', his 'unavowed theory of being', is precisely the existence of some supposed entity, in the midst of the stream of perceptions which otherwise constitute the 'person-as-bundle', with faculties of imagination and of memory, which persists through time and change, and is thus able to recognise the relations of Resemblance, Contiguity, and Constant Conjunction and employ them to develop customs, or habits, and, in turn, to form fictitious complex ideas. This complex, unified something which persists through time and change certainly seems to be a lot like a substantival mind. Thus, it is not unfair to say that the existence of substantival mind is a hidden premise in Hume’s argument.

Now, if Hume’s denial of substantival mind really does rest on the assumption of its existence, then the structure of his argument is, roughly speaking, more an example of indirect proof, or reductio ad absurdum, than of direct proof. Indirect proof is a hypothetical inference rule whereby, if, given hypothesis p, one can derive a contradiction (p & not-p), one may validly infer not-p. Hume’s denial of mind rests upon the work of the supposed faculties of memory and imagination, which seem to indicate the existence of a mind. Thus, in the present case, given Hume’s hypothesis that mind does not exist (not-m), along with its attendant assumptions, we are able to derive a contradiction (m & not-m), and may therefore dispense with the hypothesis and conclude not-not-m, or simply m, mind exists. If this is so, Hume’s work, regardless of his intentions, might be properly considered evidence more in support of substantival mind than against it.

In any case, since the assumption of this mind-like entity is involved in every act of experience, whether delusional or not, its existence and its nature deeply affect every aspect of Hume’s system. Any weakness or uncertainty in Hume’s doctrine of mind will carry significant implications for the whole of his project. By drawing attention to the difficulties surrounding Hume’s treatment of mind, I hope to have shown that a dark cloud hovers over the whole of his system.

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(1) Locke, John, Essay Concerning Human Understanding, i. i. ii.

(2) Hume, Treatise of Human Nature, Introduction.

(3) Ibid.

(4) Ibid., i. ii. vi.

(5) Ibid., i. i. i.

(6) Ibid., i. i. i.

(7) Ibid., i. i. i.

(8) Ibid., i. i. i.

(9) Ibid., i. i. i.

(10) Ibid., i. i. iv.

(11) Ibid., i. i. iv.

(12) Ibid., i. iii. ii.

(13) Ibid., i. iv. v.

(14) Strange that Hume, having dismissed the possibility of simple ideas being associated into complex by chance, should at the level of impressions have recourse to no other 'agent'. One is inclined to wonder why Hume thought it impossible that ideas should be constantly associated by chance into the same ordered pattern that we apprehend in experience, but that it is not impossible for impressions to be thus associated.

(15) Hume, Treatise of Human Nature, i. iv. v.

(16) Ibid., i. iv. v. Hume's maxim "all that is distinct is separable" and the outright neglect, in both Locke and Hume, of the modal distinction are points that cry out for criticism. However, as the thrust of this paper is limited, these will have to be covered more thoroughly elsewhere.

(17) Ibid., i. iv. vi.

(18) Ibid., i.iv.vi.

(19) Ibid., i. iv. v.

(20) Ibid., i. i. iv.; cf. note xi.

(21) Copleston, Frederick, S.J.; A History of Philosophy, Vol. VIII, p.120.

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