“Chemistry does not afford the same species of argument (in favour of design) that mechanism affords, and yet may afford an argument in a high degree satisfactory.” This remark of the excellent Paley, has been made by him with reference only to a particular subject; but the following sketch, pointing out the grounds upon which chemistry as a science is founded, and the rank which it holds among the departments of human knowledge, will at the same time, show the general truth of the remark.

An elaborate enquiry into the origin and nature of human knowledge, would be quite misplaced here. We shall content ourselves, with simply considering it of the two kinds, described in the introduction, viz.: a knowledge of what must be; that is to say, of what we cannot conceive either not to exist, or to exist otherwise than as it is; and which is therefore founded upon reason (or necessity): and a knowledge of what simply is, but how or why we know not; and for the existence of which, therefore, we have no authority beyond our own consciousness, or the evidence of our senses.

Of these, the only instance of the first kind which particularly concerns us at present, is the knowledge of quantity, and its relations in general: of the second, that of certain natural phenomena; the consideration of which, constitutes the proper subject of the present volume.