Chapter VIII

, p. 221, the distinction was drawn between two kinds of knowledge of things, bare acquaintance with them and knowledge about them. The possibility of two such knowledges depends on a fundamental psychical peculiarity which may be entitled "_the principle of constancy in the mind's meanings_" and which may be thus expressed: "_The same matters can be thought of in successive portions of the mental stream, and some of these portions can know that they mean the same matters which the other portions meant._" One might put it otherwise by saying that "_the mind can always intend, and know when it intends, to think of the Same._"

This _sense of sameness_ is the very keel and backbone of our thinking. We saw in