We have seen in Chapter XVI that a work on logic may be a comparatively simple thing. It may describe the ways in which men reason when they reason correctly, and may not go deep into metaphysical questions. On the other hand, it may be deeply metaphysical.
When we approach the part of logic which deals with the principles and methods of the sciences, this difference is forced upon our attention. One may set forth the assumptions upon which a science rests, and may describe the methods of investigation employed, without going much below the plane of common thought. As a type of such works I may mention the useful treatise by Professor Jevons cited earlier in this chapter.
On the other hand, our investigations may be more profound, and we may scrutinize the very foundations upon which a science rests. Both the other works referred to illustrate this method of procedure.
For example, in "The Grammar of Science," we find our author discussing, under the title "The Facts of Science," such problems as the following: the Reality of Things; Sense-impressions and Consciousness; the Nature of Thought; the External Universe; Sensations as the Ultimate Source of the Materials of Knowledge; and the Futility of "Things-in-themselves." The philosophical character of such discussions does not need to be pointed out at length.
[1] "The Principles Of Science," London, 1874, Preface.
[2] English translation, New York, 1905.
[3] Second edition, London, 1900.