Let us conclude these observations by a short reflection on the essence of our mind; in which I find an incomprehensible mixture of greatness and weakness. Its greatness is real: for it brings together the past and the present, without confusion; and by its reasoning penetrates into futurity. It has the idea both of bodies and spirits. Nay, it has the idea of the infinite: for it supposes and affirms all that belongs to it, and rejects and denies all that is not proper to it. If you say that the infinite is triangular, the mind will answer without hesitation, that what has no bounds can have no figure. If you desire it to assign the first of the units that make up an infinite number, it will readily answer, that there can be no beginning, end, or number in the infinite; because if one could find either a first or last unit in it, one might add some other unit to that, and consequently increase the number. Now a number cannot be infinite, when it is capable of some addition, and when a limit may be assigned to it, on the side where it may receive an increase. SECT. LI. The Mind knows the Finite only by the Idea of the Infinite. It is even in the infinite that my mind knows the finite. When we say a man is sick, we mean a man that has no health; and when we call a man weak, we mean one that has no strength. We know sickness, which is a privation of health, no other way but by representing to us health itself as a real good, of which such a man is deprived; and, in like manner, we only know weakness, by representing to us strength as a real advantage, which such a man is not master of. We know darkness, which is nothing real, only by denying, and consequently by conceiving daylight, which is most real, and most positive. In like manner we know the finite only by assigning it a bound, which is a mere negation of a greater extent; and consequently only the privation of the infinite. Now a man could never represent to himself the privation of the infinite, unless he conceived the infinite itself: just as he could not have a notion of sickness, unless he had an idea of health, of which it is only a privation. Now, whence comes that idea of the infinite in us? SECT. LII. Secondly, the Ideas of the Mind are Universal, Eternal, and Immutable.