(Modern English Summary)
The Arminians have generally not denied God's foreknowledge outright. Instead, they weaken and undermine it indirectly. They do this by denying the certainty and immutability of God's eternal decrees—the very foundation upon which divine foreknowledge rests.
Their real objection is not that God foreknows things in general. Rather, they object to God's foreknowledge of free and contingent events—that is, events that depend on the choices of rational creatures.
They do this because they hold to their long-discredited teaching that God's purposes concerning such events are temporary, conditional, and changeable. Once this principle is accepted, it becomes easy to make human free will and chance the governing principles of history rather than the sovereign providence of God.
By a contingent event, we mean something that, considered in relation to its immediate cause, may either happen or not happen before it actually occurs. For example, a man may choose tomorrow to perform a certain action—or he may choose not to perform it. From the standpoint of his own will, either outcome is possible.
In this sense, human actions are free and contingent with respect to their secondary causes—that is, with respect to the persons performing them.
Yet if we lift our eyes to God, who has foreseen and ordained either the event itself or its omission, then such things may rightly be said to occur necessarily. Once God's eternal decree is considered, the outcome could not have been otherwise than it was.
Throughout history, Christians—and even many pagans—have naturally spoken this way. When some remarkable event occurs, people instinctively acknowledge God's providence in it.
For example, suppose a man is killed when a house unexpectedly collapses upon him. From the standpoint of human freedom, he might never have been there. Yet after the event we commonly say, "It was God's will."
Likewise, if a traveler falls into the hands of robbers, we immediately conclude that it happened according to God's providence. It could not have occurred otherwise, for God knew it beforehand and ordained its place in his eternal plan.
For the sake of clarity, theologians have traditionally distinguished between two kinds of knowledge in God.
First, there is what is called God's knowledge of simple intelligence.
By this knowledge God knows all things that are possible. He sees everything that his infinite power could create or accomplish, whether or not he ever chooses to bring it into existence.
Countless things that will never actually exist are nevertheless perfectly known to God.
Could he have created another world? Certainly.
Could he have made this world differently? Without question.
Could he have chosen not to create at all? Surely.
His wisdom contains inexhaustible possibilities, and his power could produce infinitely more things than presently exist.
All such possibilities lie open before him. He knows them perfectly simply because his infinite power is capable of producing them.
Second, from this limitless realm of possibilities, God freely determines by his decree what shall actually come to pass.
Things that were merely possible become future because God wills them to be so.
Following this decree—or, more precisely, accompanying it—is what theologians call God's knowledge of vision.
By this knowledge God infallibly sees all things exactly as they will occur. He knows their causes, their circumstances, their timing, and their outcome.
The difference between these two forms of knowledge is this:
By the first, God knows everything that could happen.
By the second, he knows everything that certainly will happen.
The first is measured by God's omnipotence—what he is able to do.
The second is measured by God's decree—what he has determined to do or permit.
Therefore, God's foreknowledge extends to all things that he has decreed shall come to pass, and to nothing apart from that decree.
In carrying out his purposes, God employs different kinds of causes.
Some causes operate necessarily by the nature God has given them.
The sun gives light.
Fire gives heat.
Ordinarily, these causes act according to fixed laws established by their Creator.
Yet even these depend upon God's continual concurrence. He remains the first cause behind all secondary causes and sustains their operation according to his own free will.
This is why God could cause the sun to stand still in Joshua's day and prevent the fire from burning the three Hebrew children. Though natural causes ordinarily act in a fixed manner, God remains sovereign over them all.
Other causes are free and contingent.
Angels and human beings act through deliberation and choice. They select one course of action rather than another. In this sense, their actions are genuinely voluntary.
Other events occur accidentally from a human perspective. A man swinging an axe may unintentionally kill someone when the axe head flies off the handle.
Yet none of these events—whether necessary, free, or accidental—occur outside God's determination.
God has ordained not only that events occur, but also the manner in which they occur.
Some happen necessarily.
Some happen freely.
Some happen contingently.
Yet all possess a certain future existence because they have been included within God's decree.
For this reason, God infallibly foreknows them all.