Ordinary language confirms this truth. When there is a variation of modifications we say that the substance changes, that is, we conceive something which existed before the change, and exists after it. We say that a modification has entirely disappeared; we do not say this of the substance, but only that it is, or is presented to us, in a different manner. We therefore conceive something which remains constant and identical under different modifications: the subject in which these changes occur, this something which does not disappear with the disappearance of the modifications, which is not changed internally with these changes, we call substance, _substantia_, _substratum_. CHAPTER II. APPLICATION OF THE IDEA OF SUBSTANCE TO CORPOREAL OBJECTS. 7. Let us apply the ideas contained in that of substance to a corporeal object: this will help explain these ideas, and perhaps suggest others. The paper on which I am writing is susceptible of various modifications: I may write on it a thousand different things, in various characters, and in different colors; I may fold it in various ways, and give it an infinite variety of positions in relation to the objects around it, and I may move it in all imaginable directions. Under this infinity of changes there is something constant, something which does not change. There are many new things, but there is one which is not new, which is always the same. There is one which suffers these changes, but retains something which does not change. If I make the paper blue and then red, that which is now red is the same that was blue, and before that white, and to this which is constant all those changes are referred. If a white paper is shown me, and then another paper that is blue, and then one that is red, it is clear that it is not the same as though I gave all these transformations to the same paper. The impression which the color produces in me remains the same; in what, then, does the difference consist? The difference is, that in the one case there is something permanent, which has passed through successive changes; in the other case this _something_ is not the same, but is another and different thing. In the one case there are different modifications; in the other there are different substances.