But since it may be said that these truths are in the mind, but in such a way that it is only when they are proposed that men assent to them, Locke goes on to clinch his argument. If this be true, it shows that the ideas are not innate; for the same thing is true of a large number of scientific truths, those of mathematics and morals, as well as of purely sensible facts, as that red is not blue, sweet is not sour, etc.,--truths and facts which no one calls innate. Or if it be said that they are in the mind implicitly or potentially, Locke points out that this means either nothing at all, or else that the mind is _capable_ of knowing them. If this is what is meant by innate ideas, then all ideas are innate; for certainly it cannot be denied that the mind is capable of knowing all that it ever does know, or, as Locke ingenuously remarks, "nobody ever denied that the mind was capable of knowing several truths." It is evident that the force of Locke's contention against innate ideas rests upon a certain theory regarding the nature of innate ideas and of the relations of consciousness to intelligence. Besides this, there runs through his whole polemic the assertion that, after all, innate ideas are useless, as experience, in the sense of impressions received from without, and the formal action of intelligence upon them, is adequate to doing all they are supposed to do. It is hardly too much to say that the nerve of Locke's argument is rather in this positive assertion than in the negations which he brings against this existence. Leibniz takes issue with him on each of these three points. He has another conception of the very nature of innate ideas; he denies Locke's opinions about consciousness; he brings forward an opposed theory upon the relation of experience to reason. This last point we shall take up in a chapter by itself, as its importance extends far beyond the mere question as to the existence of ideas which may properly be called innate. The other two questions, as to the real character of innate ideas and the relation of an idea to consciousness, afford material to occupy us for the present.