Locke's account of innate ideas and of sensation is only preparatory to a discussion of the ideas got by sensation. His explanation of the mode of knowledge leads up to an explanation of the things known. He remains true to his fundamental idea that before we come to conclusions about any matters we must "examine our own ability." He deals first with ideas got by the senses, whether by some one or by their conjoint action. Of these the ideas of solidity, of extension, and of duration are of most concern to us. They form as near an approach to a general philosophy of nature as may be found anywhere in Locke. They are, too, the germ from which grew the ideas of matter, of space, and of time, which, however more comprehensive in scope and more amply worked out in detail, characterize succeeding British thought, and which are reproduced to-day by Mr. Spencer. "The idea of solidity we receive by our touch." "The ideas we get by more than one sense are of space or extension, figure, rest, and motion." These sentences contain the brief statement of the chief contention of the sensational school. Locke certainly was not conscious when he wrote them that they were the expression of ideas which should resolve the world of matter and of space into a dissolving series of accidentally associated sensations; but such was none the less the case. When he writes, "If any one asks me what solidity is, I send him to his senses to inform him," he is preparing the way for Berkeley, and for a denial of all reality beyond the feelings of the individual mind. When he says that "we get the idea of space both by sight and touch," this statement, although appearing truistic, is none the less the source of the contention of Hume that even geometry contains no necessary or universal elements, but is an account of sensible appearances, relative, as are all matters of sensation.