Classification of the sciences (Peirce)

In 1902 and 1903 Peirce elaborates classifications of the sciences in:

Peirce had already for a while divided the Sciences of Discovery into:

(1) Mathematics – draws necessary conclusions about hypothetical objects

Thus Peirce ends up framing two fields each of which is philosophy in a sense: cenoscopic philosophy which precedes the special sciences, and synthetic philosophy (that is to say, science of review), which does take advantage of the results of all the sciences of discovery and develops, for instance, classifications of the sciences.

This classification, which aims to base itself on the principal affinities of the objects classified, is concerned not with all possible sciences, nor with so many branches of knowledge, but with sciences in their present condition, as so many businesses of groups of living men. It borrows its idea from Comte's classification; namely, the idea that one science depends upon another for fundamental principles, but does not furnish such principles to that other. It turns out that in most cases the divisions are trichotomic; the First of the three members relating to universal elements or laws, the Second arranging classes of forms and seeking to bring them under universal laws, the Third going into the utmost detail, describing individual phenomena and endeavoring to explain them. But not all the divisions are of this character....

The following table is based mostly on Peirce's 1903 classification, which was more or less the final form. But see after the table for discussion of his later remarks on the divisions of logic.

Thus the three main 1903 departments of logic were now sub-departments of the study of the logic of symbols.

I have now sketched my doctrine of Logical Critic, skipping a good deal. I recognize two other parts of Logic. One which may be called Analytic examines the nature of thought, not psychologically but simply to define what it is to doubt, to believe, to learn, etc., and then to base critic on these definitions is my real method, though in this letter I have taken the third branch of logic, Methodeutic, which shows how to conduct an inquiry. This is what the greater part of my life has been devoted to, though I base it upon Critic.