52. Logical First Principles. -- We have seen that the syllogism derives its demonstrative force from a necessary proposition. Whence does this proposition derive its logical value? From a previous reasoning. We cannot go on from one process of reasoning to another indefinitely.^{1} Otherwise we should be obliged to say that no conclusion is certain. There must be propositions on which the reasonings are supported, and which themselves need no demonstration. These are called logical principles: they are the enunciation of a relation between primary notions.

There are two kinds of principles: (1) generative principles of the sciences; (2) directive principles, or axioms.

{1} Criteriology, 32-54.