Note 57 — Introductory material

We may retain, however, a distinction roughly corresponding to the Kantian à priori and à posteriori, though less rigid, and more liable to change with the degree of organisation of knowledge. Kant usually endeavoured to prove, as observed above, that his synthetic à priori propositions were necessary prerequisites of experience; now although we cannot retain the term synthetic, we can retain the term à priori, for those assumptions, or those postulates, from which alone the possibility of experience follows. Whatever can be deduced from these postulates, without the aid of the matter of experience, will also, of course, be à priori. From the standpoint of general logic, the laws of thought and the categories, with the indispensable conditions of their applicability, will be alone à priori; but from the standpoint of any special science, we may call à priori whatever renders possible the experience which forms the subject-matter of our science. In Geometry, to particularize, we may call à priori whatever renders possible experience of externality as such.