A Treatise of Human Nature · David Hume
GENERAL INTRODUCTION TO VOL. I.
325. In the passage already quoted, where Hume is speaking of the expectation in question as depending simply on habit, he yet speaks of it as an expectation ‘of the _same train of objects_ to which we have been accustomed.’ These words in effect imply that it is _not_ habit, as constituted simply by the repetition of separate sequences of feelings, that governs the expectation--in which case, as we have seen, the expectation would be made up of expectations as many and as various in strength as have been the sequences and their several degrees of regularity--but, if habit in any sense, habit as itself governed by conceptions of ‘identity and distinct continued existence,’ in virtue of which, as past experience is not an indefinite series of perishing impressions of separate men but represents one world, so all fresh experience becomes part ‘of the same train of objects;’ part of a system of which, as a whole, ‘the change lies only in the time’. [1] If now we look back to the account given of the relation of memory to belief we shall find that it is just so far as, without distinct avowal, and in violation of his principles, he makes ‘impressions of memory’ carry with them the conception of a real system, other than the consciousness of their own liveliness, that he gains a meaning for belief which makes it in any respect equivalent to the judgment, based on inference, of actual science.
That the inferred idea is a cause or effect and, as such, has ‘real existence,’ merely means that it has this derived liveliness or is believed; just as the reality ascribed to the impression of memory lies merely in its having this abundant liveliness from which to communicate to its ‘usual attendant.’ But while the title of an idea to be reckoned a cause or effect is thus made to depend on its having the derived liveliness which constitutes belief, [3] on the other hand we find Hume from time to time making belief depend on causation, as on a relation of objects distinct from the lively suggestion of one by the others. ‘Belief arises only from causation, and we can draw no inference from one object to another except they be connected by this relation.’ ‘The relation of cause and effect is requisite to persuade us of any real existence’. [4] In the context of these disturbing admissions we find a reconsideration of the doctrine of memory which explains them, but only throws back on that doctrine the inconsistency which they exhibit in the doctrine of belief. [1] Above, paragraphs 289 and ff. [2] P. 445. [Book I, part III., sec. XIII.] [3] It may be as well here to point out the inconsistency in Hume’s use of ‘belief.’ At the end of sec. 5 (Part III.) the term is extended to ‘impressions of the senses and memory.’ We are said to believe when ‘we feel an _immediate impression_ of the senses, or a repetition of that impression in the memory. But in the following section the characteristic of belief is placed in the _derived_ liveliness of an _idea_ as distinct from the immediate liveliness of impression.
The truth is implicitly recognized that the reality of an individual object consists in that system of its relations which only exists for a conceiving, as distinct from a feeling, subject, even as the unreal has no meaning except as a confused or inadequate conception of such relations; and that thus the ‘present impression’ is neither real nor unreal in itself, but may be equally one or the other according as the relations, under which it is conceived by the subject of it, correspond to those by which it is determined for a perfect intelligence. [1] [1] See above, paragraphs 184 & 183. It is constituted by relations, which are not impressions at all; and in this lies explanation of the inference from it to ‘system of judgment’.
329. A clear recognition of this truth can alone explain the nature of belief as a result of inference from the known to the unknown, which is, at the same time, inference to a matter of fact. The popular notion, of course, is that certain facts are given by feeling without inference and then other facts inferred from them. But what is ‘fact’ taken to mean? If a feeling, then an inferred fact is a contradiction, for it is an unfelt feeling. If (as should be the case) it is taken to mean the relation of a feeling to something, then it already involves inference--the interpretation of the feeling by means of the conception of a universal, self or world, brought to it--an inference which is all inference _in posse_, for it implies that a universe of relations is there, which I must know if I would know the full reality of the individual object: so that no fact can be even partially known without compelling an inference to the unknown, nor can there be any inference to the unknown without modification of what already purports to be known. Hume, trying to carry out the equivalence of fact and feeling, and having clearer sight than his masters, finds himself in the presence of this difficulty about inference.
Unless the inferred object is other than one of sense (outer or inner) or of memory, there is no reasoning, but only perception; [1] but if it is other, how can it be real or even an object of consciousness at all, since consciousness is only of impressions, stronger or fainter? The only consistent way out of the difficulty, as we have seen, is to explain inference as the expectation of the recurrence of a feeling felt before, through which the unknown becomes known merely in the sense that from the repetition of the recurrence the expectation has come to amount to the fullest assurance. But according to this explanation the difference between the inferences of the savage and those of the man of science will lie, not in the objects inferred, but in the strength of the expectation that constitutes the inference. Meanwhile, if a semblance of explanation has been given for the inference from cause to effect, that from effect to cause remains quite in the dark. How can there be inference from a given feeling to that felt immediately before it? [1] Pp. 376 & 388. [Book I, part III., secs. II. and VI.] Not seeing this, Hume has to explain inference to latter system as something forced upon us by habit.
330. From the avowal of such paradoxical results, Hume only saved himself by reverting, as in the passage before us, to the popular view--to the distinction between two ‘systems of reality,’ one perceived, the other inferred; one ‘the object of the senses and memory,’ the other ‘of the judgment.’ He sees that if the educated man erased from his knowledge upon us by of the world all ‘facts’ but those for which he has ‘the evidence of his senses and memory,’ his world would be unpeopled; but he has not the key to the true identity between the two systems. Not recognizing the inference already involved in a fact of sense or memory, he does not see that it is only a further articulation of this inference which gives the fact of judgment; that as the simplest fact for which we have the ‘evidence of sense’ is already not a feeling but an explanation of a feeling, which connects it by relations, that are not feelings, with an unfelt universe, so inferred causes and effects are explanations of these explanations, by which they are connected as mutually determinant in the one world whose presence the simplest fact, the most primary explanation of feeling, supposes no less than the most complete.
Not seeing this, what is he to make of the system of merely inferred realities? He will represent the relation of cause and effect, which connects it with the ‘system of memory,’ as a habit derived from the constant _de facto_ sequence of this or that ‘inferred’ upon this or that remembered idea. The mind, ‘feeling’ the unchangeableness of this habit, regards the idea, which in virtue of it follows upon the impression of memory, as equally real with that impression. In this he finds an answer to the two questions which he himself raises: _(a)_ ‘Why is it that we draw no inference from one object to another, except they be connected by the relation of cause and effect;’ or (which is the same, since inference to an object implies the ascription of reality to it), ‘Why is this relation requisite to persuade us of any real existence?’ and _(b)_, ‘How is it that the relations of resemblance and contiguity have not the same effect?’ The answer to the first is, that we do not ascribe reality to an idea recalled by an impression, unless we find that, owing to its customary sequence upon the impression, we cannot help passing from the one to the other. The answer to the second corresponds.
331. Now this account has the fault of being inconsistent with Hume’s primary doctrine, inasmuch as it makes the real an object of thought in distinction from feeling, without the merit of explaining the extension of knowledge beyond the objects of sense and memory. It turns upon a conception of the real, as the unchangeable, which the succession of feelings, in endless variety, neither is nor could suggest. It implies that not in themselves, but as representing such an unchangeable, are the feelings which ‘return on us whether we will or no,’ regarded as real. The peculiar sequence of one idea on another, which is supposed to constitute the relation of cause and effect, is not, according to this description of it, a sequence of feelings simply; it is a sequence reflected on, found to be unchangeable, and thus to entitle the sequent idea to the prerogative of reality previously awarded (but only by the admission as real of the ‘fiction’ of distinct continued existence) to the system of memory. But while the identification of the real with feeling is thus in effect abandoned, in saving the appearance of retaining it, Hume makes his explanation of the ‘system of judgment’ futile for its purpose. He saves the appearance by intimating that the relation of cause and effect, by which the inferred idea is connected with the idea of memory and derives reality from it, is only the repeated sequence of the one idea upon the other, of the less lively feelings upon the more lively, or a habit that results from such repetition. But if the sequence of the inferred idea upon the other must have been so often repeated in order to the existence of the relation which renders the inference possible, the inferred idea can be no new one, but must itself be an idea of memory, and the question, how any one’s knowledge comes to extend beyond the range of his memory, remains unanswered.
Nor does this merely mean that it cannot constitute new phenomena, while it can prove relations, previously unknown, between phenomena. Such a distinction inadmissible with Hume. 334. At the point which our discussion has reached, few words should be wanted to show that thus to interpret Hume is to read into him an essentially alien theory, which has doubtless grown out of his, but only by a process of adaptation which it needs a principle the opposite of his to justify. Hume, according to his own profession, knows of no objects but impressions and ideas--feelings stronger or more faint--of no reality which it needs thought, as distinct from feeling, to constitute. But a uniform relation between phenomena is neither impression nor idea, and can only exist for thought. He could not therefore admit inference to such relation as to a real existence, without a double contradiction, nor does he ever explicitly do so. He never allows that inference is other than a transition to a certain sort of feeling, or that it is other than the work of imagination, the weakened sense, as enlivened by custom to a degree that puts it _almost_ on a level with sense; which implies that in every case of inference the inferred object is _not_ a uniform relation--for how can there be an image of uniform relation?--and that it _is_ something which has been repeatedly and without exception perceived to follow another before it can be inferred.
Even when in violation of his principle he has admitted a ‘system of memory’--a system of things which have been felt, but which are not feelings, stronger or fainter, and which are what they are only through relation--he still in effect, as we have seen, makes the ‘system of judgment,’ which he speaks of as inferred from it, only the double of it. To suppose that, on the strength of a general inference, itself the result of habit, in regard to the uniformity of nature, particular inferences may be made which shall be other than repetitions of a sequence already habitually repeated, is, if there can be degrees of contradiction, even more incompatible with Hume’s principles than to suppose such inferences without it. If a uniformity of relation between particular phenomena is neither impression nor idea, even less so is the system of all relations. His distinction of probability of causes from that of chances might seem to imply conception of nature, as determining inference.
335. There is language, however, in the chapters on ‘Probability of Chances and of Causes,’ which at first sight might seem to warrant the ascription of such a supposition to Hume. According to the distinction which he inherited from Locke all inference to or from causes or effects, since it does not consist in any comparison of the related ideas, should be merely probable. And as such he often speaks of it. His originality lies in his effort to explain what Locke had named; in his treating that ‘something not joined on both sides to, and so not showing the agreement or disagreement of, the ideas under consideration’ which yet ‘makes me believe’, [1] definitely as Habit. But ‘in common discourse,’ as he remarks, ‘we readily affirm that many arguments from causation exceed probability’; [2] the explanation being that in these cases the habit which determines the transition from impression to idea is ‘full and perfect.’ There has been enough past experience of the immediate sequence of the one ‘perception’ on the other to form the habit, and there has been no exception to it. In these cases the ‘assurance,’ though distinct from knowledge, may be fitly styled ‘proof,’ the term ‘probability’ being confined to those in which the assurance is not complete.
Hume thus comes to use ‘probability’ as equivalent to incompleteness of assurance, and in this sense speaks of it as ‘derived either from imperfect experience, or from contrary causes, or from analogy’. [3] It is derived from analogy when the present impression, which is needed to give vivacity to the ‘related idea,’ is not perfectly like the impressions with which the idea has been previously found united; ‘from contrary causes,’ when there have been exceptions to the immediate sequence or antecedence of the one perception to the other; ‘from imperfect experience’ when, though there have been no exceptions, there has not been enough experience of the sequence to form a ‘full and perfect habit of transition.’ Of this last ‘species of probability,’ Hume says that it is a kind which, ‘though it naturally takes place before any entire proof can exist, yet no one who is arrived at the age of maturity can any longer be acquainted with. ’Tis true, nothing is more common than for people of the most advanced knowledge to have attained only an imperfect experience of many particular events; which naturally produces only an imperfect habit and transition; but then we must consider that the mind, having formed another observation concerning the connexion of causes and effects, gives new force to its reasoning from that observation; and by means of it can build an argument on one single experiment, when duly prepared and examined. What we have found once to follow from any object we conclude will for ever follow from it; and if this maxim be not always built upon as certain, ’tis not for want of a sufficient number of experiments, but because we frequently meet with instances to the contrary’--which give rise to the other sort of weakened assurance or probability, that from ‘contrary causes’. [4]
In other words, they represent the notion of that ‘continued existence distinct from our perceptions,’ which with Hume is a phrase generated by ‘propensities to feign.’ Yet he does not profess to reject them; nay, he handles them as if they were his own, but after a very little of his manipulation they are so ‘translated’ that they would not know themselves. Because philosophers ‘allow that what the vulgar call chance is nothing but a concealed cause,’ ‘probability of causes’ and ‘probability of chances’ may be taken as equivalent. But chance, as ‘merely negation of a cause,’ has been previously explained, on the supposition that causation means a ‘perfect habit of imagination,’ to be the absence of such habit--the state in which imagination is perfectly indifferent in regard to the transition from a given impression to an idea, because the transition has not been repeated often enough to form even the beginning of a habit. Such being mere chance, ‘probability of chances’ means a state of imagination between the perfect indifference and that perfect habit of transition, which is ‘necessary connexion.’ ‘Probability of causes’ is the same thing. Its strength or weakness depends simply on the proportion between the number of experiments (‘each experiment being a kind of chance’) in which A has been found to immediately follow B, and the number of those in which it has not. [2] Mere chance, probability, and causation then are equally states of imagination. The ‘equal necessity of the connexion between all causes and effects’ means not that any ‘law of causation pervades the universe,’ but that, unless the habit of transition between any feelings is ‘full and perfect,’ we do not speak of these feelings as related in the way of cause and effect.
Experience, according to his account of it, cannot be a parent of knowledge. 338. The case then stands thus. In order to make the required distinction between inference to real existence and the lively suggestion of an idea, Hume has to graft on his theory the alien notion of an objective system, an order of nature, represented by ideas of memory, and on the strength of such a notion to interpret a transition from these ideas to others, because we cannot help making it, as an objective necessity. Of such alien notion and interpretation he avails himself in his definition (understood as he means it to be understood) of cause as a ‘natural relation’. [1] But he had not the boldness of his later disciples. Though he could be inconsistent so far, he could not be inconsistent far enough to make his theory of inference fit the practice of natural philosophers. Bound by his doctrine of ideas as copied from impressions, he can give no account of inferred ideas that shall explain the extension of knowledge beyond the expectation that we shall feel again what we have felt already. It was not till another theory of experience was forthcoming than that given by the philosophers who were most fond of declaring their devotion to it, that the procedure of science could be justified.
The old philosophy, we are often truly told, had been barren for want of contact with fact. It sought truth by a process which really consisted in evolving the ‘connotation’ of general names. The new birth came when the mind had learnt to leave the idols of the tribe and cave, and to cleave solely to experience. If the old philosophy, however, was superseded by science, science itself required a new philosophy to answer the question. What constitutes experience? It was in effect to answer this question that Locke and Hume wrote, and it is the condemnation of their doctrine that, according to it, experience is not a possible parent of science. It is not those, we know, who cry ‘Lord, Lord!’ the loudest, that enter into the kingdom of heaven, nor does the strongest assertion of our dependence on experience imply a true insight into its nature. Hume has found acceptance with men of science as the great exponent of the doctrine that there can be no new knowledge without new experience. It has not been noticed that with him such ‘new experience’ could only mean a further repetition of familiar feelings, and that if it means more to his followers, it is only because they have been less faithful than he was to that antithesis between thought and reality which they are not less loud in asserting.
If that thinking substance, the survival of which was the condition of his theory serving its theological purpose, [4] is to survive at all, it can only be as equivalent to Spinoza’s substance, in which ‘both matter and thought were supposed to inhere.’ The universe of our experience--‘the sun, moon, and stars; the earth, seas, plants, animals, men, ships, houses, and other productions, either of art or nature’--is the same universe when it is called ‘the universe of objects or of body,’ and when it is called ‘the universe of thought, or of impressions and ideas;’ but to hold, according to Spinoza’s ‘hideous hypothesis,’ that ‘the universe of objects or of body’ inheres in one simple uncompounded substance, is to rouse ‘a hundred voices of scorn and detestation;’ while the same hypothesis in regard to the ‘universe of impressions and ideas’ is treated ‘with applause and veneration.’ It was to save God and Immortality that the ‘great philosopher,’ who had found the true way out of the scholastic absurdity of abstract ideas, [5] had yet clung to the ‘unintelligible chimaera’ of thinking substance; and after all, in doing so, he fell into a ‘true atheism,’ indistinguishable from that which had rendered the unbelieving Jew ‘so universally infamous’. [6] [1] See above, par. 177. [2] Pp. 520-521. [Book I, part IV., sec. V.]
Nor, since causation merely means the constant conjunction of impressions, and there is no such contrariety between the impression we call ‘motion of matter’ and that we call ‘thought,’ anymore than between any other impressions, [2] as is incompatible with their constant conjunction, is there any reason why we should set aside the hourly experience, which tells us that bodily motions are the cause of thoughts and sentiments. If, however, there were that necessary connexion between effect and cause, by which Locke sought to show the spirituality of the first cause, it would really go to show just the reverse of infinite power in such cause. It is from our impressions and ideas that we are supposed to infer this cause; but in these--as Berkeley had shown, and shown as his way of proving the existence of God--there is no efficacy whatever. They are ‘inert.’ If then the cause must agree with the effect, the Supreme Being, as the cause of our impressions and ideas, must be ‘inert’ likewise. If, on the other hand, with Berkeley we cling to the notion that there must be efficient power somewhere, and having excluded it from the relation of ideas to each other or of matter to ideas, find it in the direct relation of God to ideas, we fall ‘into the grossest impieties;’ for it will follow that God ‘is the author of all our volitions and impressions.’ [3]
342. Against the doctrine of a real ‘identity of the self or person’ Hume had merely to exhibit the contradictions which Locke’s own statement of it involves. [1] To have transferred this identity definitely from ‘matter’ to consciousness was in itself a great merit, but, so transferred, in the absence of any other theory of consciousness than Locke’s, it only becomes more obviously a fiction. If there is nothing real but the succession of feelings, identity of body, it is true, disappears as inevitably as identity of mind; and so we have already found it to do in Hume. [2] But whereas the notion of a unity of body throughout the succession of perceptions only becomes contradictory through the medium of a reduction of body to a succession of perceptions, the identity of a mind, which has been already defined as a succession of perceptions, is a contradiction in terms. There can be ‘properly no simplicity in it at one time, nor identity at different; it is a kind of theatre where several perceptions successively make their appearance.’ But this comparison must not mislead us. ‘They are the successive perceptions only, that constitute the mind; nor have we the most distant notion of the place where these scenes are represented, or of the materials of which it is composed.’ The problem for Hume then in regard to personal, as it had been in regard to bodily, identity is to account for that ‘natural propension to imagine’ it which language implies.
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