It has been said that “knowledge is power;” but it is not implied by that expression that it is a power capable of exerting itself. All that is implied is, that it directs an active agent in the manner of exerting his power. What effect, I would ask, can my knowledge of a past event have upon that event? Surely none at all. What effect can my knowledge of a future event have upon it? Considered in itself, it can have no influence at all. Is there any event, whether past, present, or future, on which the mere knowledge of man can have any influence? Certainly there is none. Knowledge is something existing in the mind. It has its seat there, and of itself it is incapable of walking abroad to act upon extraneous objects. I would therefore ask, What effect can the divine knowledge have on a past or present event? Is it not obvious that it can have none? The knowledge of God does not affect the faithfulness of Abraham, or the treachery of Judas, in the least. Those events would still continue to have occurred precisely as they did, if we could suppose all trace of them to be erased from the divine mind. And if we could suppose that God was not now looking down upon me, could any one believe that I would write with any more or less freedom on that account? Surely not. If, then, knowledge, considered in all these different aspects, is passive in its nature, how can we rationally infer that its passivity is converted into activity so soon as we view it in the aspect of the divine prescience?
But it will doubtless be argued that although the foreknowledge of God may not render future events necessary, yet it proves that they are so. To this we reply, that it proves that they are certain, but cannot prove that they are necessary. But still, it will be asked, where is the difference? If they are certain, must they not therefore be necessary?
That we may illustrate the distinction between certainty and necessity, we will refer to the crime of Judas in betraying the Saviour. Here we would say it was a matter certain in the divine mind, from all eternity, that Judas would commit this crime. God foreknew it. Although it was also foretold, yet it was not rendered any the more certain by that circumstance; for prediction is only knowledge recorded or made manifest; but knowledge is equally certain, whether secret or revealed. The pointed question now is, Could Judas possibly have avoided that crime? Was he still a free agent? and might he have acted differently? or was he impelled by absolute necessity? We answer, he could have avoided the crime. He was still a free agent, and might have acted differently.
Here it will no doubt be argued that if he had avoided the crime, the foreknowledge of God would have been defeated, and the Scriptures broken. To fairly solve this difficulty, and draw the line between certainty and necessity, we answer, that if Judas, in the exercise of the power of free agency with which he was endued, had proved faithful, and avoided the crime in question, neither would the foreknowledge of God have been frustrated, nor the Scriptures broken. In that case, the foreknowledge of God would have been different, accordingly as the subject varied upon which it was exercised. God could not then have foreknown his treachery; and had it not been foreknown, it never could have been predicted. A free agent may falsify a proposition supposed to announce foreknowledge, but cannot falsify foreknowledge; for if the agent should falsify the proposition, that proposition never could have been the announcement of foreknowledge.
The truth is, the prediction depends on the foreknowledge, and the foreknowledge on the event itself. The error of the necessitarians on this subject is, they put the effect for the cause, and the cause for the effect. They make the foreknowledge the cause of the event, whereas the event is the cause of the foreknowledge. No event ever took place merely because God foreknew it; on the contrary, the taking place of the event is the cause of his having foreknown it. Let this distinction be kept in mind, that, in the order of nature, the event does not depend on the knowledge of it, but the knowledge on the event, and we may readily see a distinction between certainty and necessity. It is certain with God who will be saved, and who will not; yet it is likewise certain that salvation is made possible to many who, according to the certain prescience of God, never will embrace it. God has made some things necessary, and some things contingent. Necessary events he foreknew as necessary – that is, he foreknew that they could not possibly take place otherwise. Contingent events he foreknew as contingent – that is, he foreknew that they might take place otherwise. And thus, we think, foreknowledge and free agency may be harmonized, human responsibility maintained, and the divine government successfully vindicated. (Elements of Divinity, pp. 199-203, Wesleyan Heritage Collection CD)
You can read the full section here: Thomas Ralston on Freedom of the Will Part 8: Can Free Agency be Harmonized With Divine Foreknowledge?