"Scholium I.--I do not doubt but that to all who judge confusedly of things, and are not wont to inquire into first causes, it will be difficult to admit the demonstration of prop. 7, because they do not sufficiently distinguish between the modifications of substances, and substances themselves, and are ignorant of the manner in which things are produced. Hence it follows, that the commencement which they see natural things have, they attribute to substances; for he who knows not the true cause of things, confounds all things, and feigns that trees talk like men; that men are formed from stones as well as from seeds, and that all forms can be changed into all other forms. So, also, those who confound the divine nature with the human, naturally attribute human affections to God, especially as they are ignorant of how these affections are produced in the mind. If men attended to the nature of substance, they would not, in the least, doubt proposition seven; nay, this proposition would be an axiom to all, and would be numbered among common notions. For by substance they would understand that which exists in itself, and is concerned through itself--_i.e._, the knowledge of which does not require the knowledge of anything as antecedent to it. But by modification they would understand that which is in another thing, the conception of which is formed by the conception of the thing in which it is, or to which it belongs. We can have, therefore, correct ideas of non-existent modifications, because, although out of the understanding they have no reality, yet their essence is so comprehended in that of another, that they can be conceived through this other. The truth of substance (out of the understanding) lies nowhere but in itself, because it is conceived _per se_. If therefore any one says he has a clear idea of substance, and yet doubt whether such substance exist, this would be as much as to say that he has a true idea, and nevertheless doubts whether it be not false (as a little attention sufficiently manifests;) or if any man affirms substance to be created, he at the same time affirms that a true idea has become false, than which nothing can be more absurd. Hence it is necessarily confessed that the existence of substance, as well as its essence, is an eternal truth. And hence we must conclude that there is only one substance possessing the same attribute, which requires here a fuller development. I note therefore--1. That the correct definition of a thing includes and expresses nothing but the nature of the thing defined. From which follows--2. That no definition includes or expresses a distinct number of individuals, because it expresses nothing but the nature of the thing defined; _ergo_, the definition of a triangle expresses no more than the nature of a triangle, and not any fixed number of triangles. 3. There must necessarily be a distinct cause for the existence of every existing thing. 4.