50. This explains how the idea of time is found in almost all our conceptions, and is expressed in all languages. Man continually perceives being and not-being in all around him. He perceives it within him, in the multitude of his thoughts and affections; at one time agreeing, at another disagreeing; sometimes connected, and sometimes separated; but always distinguished from one another, always producing different modifications in the mind: they therefore exclude each other, and cannot co-exist; because the existence of one excludes the existence of the other. CHAPTER VIII. WHAT IS CO-EXISTENCE? 51. If the succession of time involves exclusion, there must be co-existence where there is no exclusion: therefore, supposing that God has created other worlds, they must necessarily be contemporaneous with the present; for it is evident that they would not be excluded; and as they have not the mutual relation of cause and effect like the phenomena of the present world, we cannot apply to them the explanation which we gave to show that the motion of the plants of Paradise was not contemporaneous with the motion of the plants in our gardens. We must, therefore, hold that it would have been impossible for another world to exist before the present world; and that though God might create as many beings as he pleased, yet, so long as they do not exclude each other, they must be contemporaneous. 52. This difficulty is not easy to solve, unless we have perfectly understood the meaning of the word exclusion. By exclusion is meant, not only the intrinsical repugnance of one being to another, but that, for one reason or another, whether intrinsical or extrinsical, the existence of one implies the negation of the existence of the other. This explanation solves the difficulty. 53. Two worlds, entirely independent of one another, could have been subjected to this exclusion by the will of God. God can create one without creating the other; in this case, we find the existence of the first and the negation of the existence of the other. God can cease to preserve the first, and create the second; we then find the existence of the second and the negation of the first. In both these cases, there is _before_ and _after_, a succession in existence. God can create both; we can conceive the existence of both without the negation of the existence of either; this is co-existence.