[AG] _Reid's Works_, p. 839. [AH] We have been content to argue this question, as Mr. Mill himself argues it, on the supposition that Sir W. Hamilton held that we are directly percipient of primary qualities in external bodies. Strictly speaking, however, Hamilton held that the primary qualities are immediately perceived only in our organism as extended, and inferred to exist in extra-organic bodies. The external world is immediately apprehended only in its secundo-primary character, as resisting our locomotive energy. But as the organism, in this theory, is a material _non-ego_ equally with the rest of matter, and as to press this distinction would only affect the verbal accuracy, not the substantial justice, of Mr. Mill's criticisms, we have preferred to meet him on the ground he has himself chosen. The same error, of supposing that "presentationism" is identical with "noumenalism," and "phenomenalism" with "representationism," runs through the whole of Mr. Stirling's recent criticism of Hamilton's theory of perception. It is curious, however, that the very passage (_Lectures_, i., p. 146) which Mr. Mill cites as proving that Hamilton, in spite of his professed phenomenalism, was an unconscious noumenalist, is employed by Mr. Stirling to prove that, in spite of his professed presentationism, he was an unconscious representationist. The two critics tilt at Hamilton from opposite quarters: he has only to stand aside and let them run against each other. Under this explanation, it is manifest that the doctrine, that matter as a subject or substratum of attributes is unknown and unknowable, is totally different from that of cosmothetic idealism, with which Mr Mill confounds it;[AI] and that a philosopher may without inconsistency accept the former and reject the latter. The former, while it holds the material substance to be unknown, does not deny that some of the attributes of matter are perceived immediately as material, though, it may be, modified by contact with mind. The latter maintains that the attributes, as well as the substance, are not perceived immediately as material, but mediately through the intervention of immaterial representatives. It is also manifest that, in answer to Mr. Mill's question, which of Hamilton's two "cardinal doctrines," Relativity or Natural Realism, "is to be taken in a non-natural sense,"[AJ] we must say, neither. The two doctrines are quite compatible with each other, and neither requires a non-natural interpretation to reconcile it to its companion. [AI] _Examination_, p. 23. [AJ] _Examination_, p. 20.