popular.[1] In place of Part II of the Treatise, there are in the Inquiry a brief reference to mathematics in the beginning of section iv, and a few remarks on space and time and the contradictions in mathematical reasonings in the second part of section xii. And in place of Part IV of the Treatise, there is section xii of the Inquiry. But although this last section deals to some extent with the same subjects as does Part IV, it is in no respect an adequate reproduction, or even summary, of its corresponding part in the Treatise. These omissions in the Inquiry are compensated, though only in a small degree, by the introduction of some new material, sections x and xi; and by the transference of the discussion on liberty and necessity from the second book of the Treatise of Human Nature to the more suitable place in the Inquiry, immediately after the treatment of causation, where it forms a complete section by itself, section viii. These additions were most likely for the purpose of stirring up the "zealots," and obtaining notoriety for the author.[2] And the omissions were probably for the sake of brevity and popular treatment.[3]
III. Particular Relations with regard to Matter:—
1. Possibility of Metaphysics and of Science. Concerning the question of the possibility of metaphysics, as a science of first principles, both works are agreed that a metaphysics is impossible.[4] But on this question the position of the Treatise is much more dogmatic than that of the Inquiry. There are some passages in the later work that seem to imply the possibility of a metaphysics,[5] but I do not think that Hume means to make such an admission. When he ventures to express the hope that philosophy may "discover, at least in some degree, the secret springs and principles, by which the human mind is actuated in its operations,"[6] he probably means such principles as custom or association of ideas, which he sometimes speaks of as ultimate principles of human nature,[7] and whose modes of operation he tries, "at least in some degree," to explain.
