Treatise is a difficult book to read, the Inquiry is a comparatively easy one.[1] With regard to arrangement, Burton[2] says of the Treatise, that "it has neither a definite and comprehensive plan, nor a logical arrangement," while Professor Adamson[3] declares: "The course of Hume's work follows immediately from his fundamental principle, and the several divisions of the treatise, so far as its theoretical portions are concerned, are but its logical consequences." Taking particular parts or subjects, the former statement is very often true; but taking the work as a whole, the latter is more nearly correct.[4] In the Inquiry, so far as it is merely a recast of the Treatise, the order of arrangement is almost precisely the same as that of the earlier work. In the Treatise there are also points of transition between the principal divisions. Thus the last section of Part I deals with abstract ideas, as if a preparation for the discussion that follows in Part II. The last section of Part II treats of the ideas of existence and external existence, being a sort of introduction to Parts III and IV. And the last section of Part III deals with the reason of animals, being a preparation for the skepticism of Part IV. These points of transition are not observable in the later work. Abstract ideas are not treated here until we come to the last section, and even then only incidentally. The ideas of existence and external existence are scarcely mentioned at all. And the section on the reason of animals appears entirely cut off from related questions by new material introduced. But we have now passed to the next heading.
II. General Relations with regard to Matter. The Inquiry is not a re-statement of the Treatise, nor is it an abridgment of the Treatise, but only of parts of it,—Parts I and III. It appears, however, that Part II also was re-written, but the monograph was never published.[5] As Professor Grose suggests, probably Hume despaired of making the subject
