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 that a function should be mental for it to be a priori. The identification of the a priori with the mental is entirely gratuitous. We should here draw a distinction between the two senses of the a priori: anteriority and superiority.

A simple physical mechanism may be a priori, in the sense of anteriority. A house is a priori, in regard to the lodgers it receives; this book is a priori, in regard to its future readers. There is no difficulty in imagining the structure of our nervous system to be a priori, in regard to the excitements which are propagated in it. A nerve cell is formed, with its protoplasm, its nucleus and its nucleoli before being irritated; its properties precede its functions. If it be possible to admit that as a consequence of ancestral experiences the function has created the organ, the latter is now formed, and this it is which in its turn becomes anterior to the function. The notion of a priori has therefore nothing in it which is repugnant to physical nature.

Let us now take the a priori in the sense of superiority. Certain judgments of ours are, we are told, universal and necessary, and through this double character go beyond the evidence of experience. This is an exact fact which deserves to be explained, but it is not indispensable to explain it by allowing to the consciousness a source of special cognitions. The English school of