skeptics on this subject. Still there is strong ground for those who claim that Hume in both the Treatise and Inquiry implies the existence of an external world independent of our perceptions. Thus Mr. Hunt[1] says that Hume "believed in an external world as much as the most ordinary individual who puts his foot on this firm earth." Of course Hume believed in the existence of an external world, after a fashion, according to his own theory. But the question is, Did he believe that this instinctive, irrational belief was true or false? It is true he often does imply the existence of an external world[2]—could not easily avoid it, especially when speaking with the vulgar.[3] This kind of reasoning, however, does not go far in philosophy. On the other hand, we have in the Treatise,[4] Hume's very elaborate account of the derivation of the idea of external existence; and of the cause of our belief in this kind of existence. Now after this process of derivation, Hume ought logically—according to the law of parsimony—to have denied the existence of an external world. Why he did not, I certainly cannot say. Perhaps he thought it useless; perhaps he thought it unnecessary. But since he omitted this process of derivation in the Inquiry, those who take the Inquiry by itself have here a good reason for asserting that, in this particular, it is more positive than the Treatise. I cannot but think, however, that if the Inquiry be interpreted in the light of the Treatise, this greater degree of positiveness entirely disappears.
8. The Existence of Spiritual Substance, Personal Identity, and Immortality of the Soul. The ideas of spiritual substance and personal identity are briefly discussed in the Appendix[5] without any change of view from that of the Treatise, but with the result that an open contradiction is brought out in Hume's fundamental principles, a contradiction which he admits he is unable to reconcile. Spiritual substance and personal identity are not discussed in the Inquiry, but the same view here as in
