120. Locke, as we have seen, after all the encroachments made unawares by thought within the limits of that experience which he opposes to it--or, to put it conversely, after all that he allows ‘nature’ to take without acknowledgment from ‘mind’--is still so far faithful to the opposition as to ‘suspect a science of nature to be impossible.’ This suspicion, which is but a hesitating expression of the doctrine that general propositions concerning substances are merely verbal, is the exact counterpart of the doctrine pronounced without hesitation that mathematical truths, being at once real and general, do not concern nature at all. Real knowledge concerning nature being given by single impressions of bodies at single times operating upon us, and by consequence being expressible only in singular propositions, any reality which general propositions state must belong merely to the mind, and a mind which can originate a reality other than nature’s cannot be a passive receptacle of natural impressions. Locke admits the real generality of mathematical truths, but does not face its consequences. Hume, seeing the difficulty, will not admit the real generality. The modern Logic, founded on Locke, believing in the possibility of propositions at once real and general concerning nature. does not see the difficulty at all. It reckons mathematical to be the same in kind with natural knowledge, each alike being real notwithstanding its generality; not aware that by so doing, instead of getting rid, as it fancies, of the originative function of thought in respect of mathematical knowledge, it only necessitates the supposition of its being originative in respect of the knowledge of nature as well. Ambiguity as to real essence causes like ambiguity as to science of nature. Particular experiment cannot afford general knowledge.