339. From the point that our enquiry has reached, we can anticipate the line which Hume could not but take in regard to Self and God. His scepticism lay ready to his hand in the incompatibility between the principles of Locke and that doctrine of ‘thinking substance,’ which Locke and Berkeley alike maintained. If the reader will revert to the previous part of this introduction, in which that doctrine was discussed, [1] he will find it equally a commentary upon those sections of the ‘Treatise on Human Nature’ which deal with ‘immateriality of the soul’ and ‘personal identity.’ Substance, we saw, alike as ‘extended’ and as ‘thinking,’ was a ‘creation of the mind,’ yet real; something of which there was an ‘idea,’ but of which nothing could be said but that it was not an ‘idea.’ The ‘thinking’ substance, moreover, was at a special disadvantage in contrast with the ‘extended,’ because, in the first place, it could not, like body, be represented as given to consciousness in the feeling of solidity, and secondly it was not wanted. It was a mere double of the extended substance to which, as the ‘something wherein they do subsist and from which they do result’ our ideas had already been referred. Having no conception, then, of Spirit or Self before him but that of the thinking substance, of which Berkeley had confessed that it was not a possible idea or object of an idea, Hume had only to apply the method, by which Berkeley himself had disposed of extended substance, to get rid of Spirit likewise. This could be done in a sentence, [2] but having done it, Hume is at further pains to show that immateriality, simplicity, and identity cannot be ascribed to the soul; as if there were a soul left to which anything could be ascribed.
[1] Above, paragraphs 127-135, 144-146, & 192.
[2] P. 517. [Book I, part IV., sec. V.]
As to Immateriality of the Soul, he plays off Locke and Berkeley against each other, and proves Berkeley a Spinozist.
340. There were two ways of conceiving the soul as immaterial, of which Hume was cognizant. One, current among the theologians and ordinary Cartesians and adopted by Locke, distinguishing extension and thought as severally divisible and indivisible, supposed separate substances—matter and the soul—to which these attributes, incapable of ‘local conjunction,’ severally belonged. The other, Berkeley’s, having ostensibly reduced extended matter to a succession of feelings, took the exclusion of all ‘matter’ to which thought could be ‘joined’ as a proof that the soul was immaterial. Hume, with cool ingenuity, turns each doctrine to account against the other. From Berkeley he accepts the reduction of sensible things to sensations. Our feelings do not represent extended objects other than themselves; but we cannot admit this without acknowledging the consequence, as Berkeley himself implicitly did, [1] that certain of our impressions—those of sight and touch—are themselves extended. What then becomes of the doctrine, that the soul must be immaterial because thought is not extended, and cannot be joined to what is so? Thought means the succession of impressions. Of these some, though the smaller number, are actually extended; and those that are not so are united to those that are by the ‘natural relations’ of resemblance and of contiguity in time of appearance, and by the consequent relation of cause and effect. [2] The relation of local conjunction, it is true, can only obtain between impressions which are alike extended. The ascription of it to such as are unextended arises from the ‘propensity in human nature, when objects are united by any relation, to add some new relation in order to complete the union’. [3] This admission, however, can yield no triumph to those who hold that thought can only be joined to a ‘simple and indivisible substance.’ If the existence of unextended impressions requires the supposition of a thinking substance ‘simple and indivisible,’ the existence of extended ones must equally imply a thinking substance that has all the properties of extended objects. If it is absurd to suppose that perceptions which are unextended can belong to a substance which is extended, it is equally absurd to suppose that perceptions which are extended can belong to a substance that is not so. Thus Berkeley’s criticism has indeed prevailed against the vulgar notion of a material substance as opposed to a thinking one, but meanwhile he is himself ‘hoist with his own petard.’ 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.]
[3] P. 521. [Book I, part IV., sec. V.]
[4] See page 325. [Book I, part I., sec. VII.]
[5] See above, paragraphs 191 and foll.