The ground on which human volitions can be foreseen, is no less plain and reasonable. In the first place, future contingent volitions are never without a cause and sufficient ground of their existence, the individual will being always taken as the cause and sufficient ground of the individual volitions. God has therefore provided for the possible existence of volitions other than his own, in the creation and constitution of finite free will. Now, in relation to him, it is not required to conceive of _media_ by which all the particular volitions may be made known or proved to his mind, previous to their actual existence. Whatever he knows, he knows by direct and infinite intuition; he cannot be dependent upon any media for his knowledge. It is enough, as I have already shown, to assign him prescience, in order to bring within his positive knowledge all future contingent volitions. He knows all the variety and the full extent of the possible, and amid the possible he foresees the actual; and he foresees not only that class of the actual which, as decreed and determined by himself, is relatively necessary, but also that class of the actual which is to spring up under the characteristic of contingency. And herein, I would remark, lies the superiority of the divine prescience over human forecast,--in that the former penetrates the contingent as accurately as the necessary. With the latter it is far otherwise. Human forecast or calculation can foresee the motions of the planets, eclipses of the sun and moon, and even the flight of the comets, because they are governed by necessary laws; but the volitions of the human will form the subject of only _probable_ calculations. But if human volitions, as contingent, form the subject of probable calculations, there must be in opposition to Edwards something "that is evident" and "now existent, with which the future existence of the _contingent_ event is connected." There are three kinds of certainty. _First_, absolute certainty. This is the certainty which lies in necessary and eternal principles e. g. 2 x 2=4; the existence of space; every body must be in space; every phenomenon must have a cause; the being of God. Logical certainty, that is, the connexion between premises and conclusion, is likewise absolute. _Secondly_. Physical certainty. This is the certainty which lies in the connexion between physical causes and their phenomena: e. g. gravitation, heat, chemical affinities in general, mechanical forces. The reason conceives of these causes as inherently active and uniform; and hence, wherever a physical cause exists, we expect its proper phenomena.