16. I am aware that the explanation which I have given, may naturally provoke the opponents of the doctrine of scientific necessity to repeat their ordinary fundamental objections, in a form adapted to the expressions which I have used. They may say, the fact that these so-called Axioms thus become evident only during the progress of experience, proves that they are derived from experience: they may, in reply to our image, say, that truths are stuck into the mind by experience, as seeds are stuck into the ground; and that to maintain that they can grow under any other conditions, is to hold the doctrine of spontaneous generation, which is equally untenable in the intellectual and in the physical world. I shall not however here resume the general discussion; but shall only say briefly in reply, that Axioms,--for instance, this Axiom, that _material substances cannot be created or annihilated by any process which we can apply_,--though it becomes evident in the progress of experience, cannot be derived from experience; for it is a proposition which never has nor can be proved by experience; but which, nevertheless, has been always assumed by men, seeking for general truths, as necessarily true, and as controlling and correcting all possible experience. And with regard to the image of vegetable development, I may say, that as such development implies both inherent forms in the living seed, and nutritive powers in earth and air; so the development of our scientific ideas implies both a formative power, and materials acted on; and that, though the analogy must be very defective, we conceive that we best follow it by placing the formative power in the living mind, and in the external world the materials acted on: while the doctrine that all truth is derived from experience only, appears to reject altogether one of these elements, or to assert the two to be one. FOOTNOTES: [Footnote 307: The remarks contained in this chapter have for the most part been already printed and circulated in a _Letter to the Author of Prolegomena Logica_, 1852.] [Footnote 308: _Biographical History of Philosophy_, 1846. In a more recent edition the author of this work has modified his expressions, but still employs himself in arguing against Dr. Whewell, in order to overthrow Kant. So far as his arguments affect my philosophy, they are, as I conceive, answered in the various expositions which I have given of that philosophy.] [Footnote 309: B. ii. The Philosophy of the Pure Sciences. Chap. ii. Of the Idea of Space. Chap. iii. Of some peculiarities of the Idea of Space. Chap. vii. Of the Idea of Time. Chap. viii. Of some peculiarities of the Idea of Time.] [Footnote 310: _Prolegomena Logica_, by H. L. Mansel, M.A. 1851.] [Footnote 311: _Logic_, i. p. 273, 3rd edit.] [Footnote 312: No. 193, p. 29.] [Footnote 313: _Prol. Log._ p. 123.] [Footnote 314: See _Phil. Ind. Sc._ b. vi. c. iii.] [Footnote 315: Kant.]