45. Thus God alone (or the necessary Being) possesses this privilege, that he must exist if possible; and since nothing can hinder the possibility of that which includes no bounds, no negation, and consequently no contradiction, that alone is sufficient to establish the existence of God _a priori_. We have likewise proved it by the reality of eternal truths. But we have also just proved it _a posteriori_ by showing that, since contingent beings exist, they can have their ultimate and sufficient reason only in some necessary Being, who contains the reason of his existence in himself. 46. Nevertheless, we must not suppose, with some, that eternal verities, being dependent upon God, are arbitrary, and depend upon his will, as Des Cartes, and afterward M. Poiret, appear to have conceived. This is true only of contingent truths, the principle of which is fitness, or the choice of the best; whereas necessary truths depend solely on His understanding, and are its internal object. 47. Thus God alone is the primitive Unity, or the simple original substance of which all the created or derived Monads are the products; and they are generated, so to speak, by continual fulgurations of the Divinity, from moment to moment, bounded by the receptivity of the creature, of whose existence limitation is an essential condition. 48. In God is _Power_, which is the source of all; then Knowledge, which contains the detail of Ideas; and, finally, Will, which generates changes or products according to the principle of optimism. And this answers to what, in created Monads, constitutes the subject or the basis, the perceptive and the appetitive faculty. But in God these attributes are absolutely infinite or perfect, and in the created Monads, or in the Entelechies (or _perfectihabiis_, as Hermolaus Barbarus translates this word), they are only imitations according to the measure of their perfection. 49. The creature is said to act externally, in so far as it possesses perfection, and to suffer from another (creature) so far as it is imperfect. So we ascribe action to the Monad, so far as it has distinct perceptions, and passion, so far as its perceptions are confused. 50. And one creature is more perfect than another, in this: that we find in it that which serves to account _a priori_ for what passes in the other; and it is therefore said to act upon the other. 51. But in simple substances this is merely an ideal influence of one Monad upon another, which can pass into effect only by the intervention of God, inasmuch as in the ideas of God one Monad has a right to demand that God, in regulating the rest from the commencement of things, shall have regard to it; for since a created Monad can have no physical influence on the interior of another, it is only by this means that one can be dependent on another.