Foreknowledge is not predestination. Actually, IT IS! :) I could have sworn there was a good Warfield piece on this, but regrettably, I couldn't find it. The following is the next best I could do. It is excerpts from Reformed Doctrine of Predestination -- Chapter VI - The Foreknowledge of God . (This is from "The Reformed Presbyterian Church" in Bloomington, IN.:
The Arminian objection against foreordination bears with equal force against the foreknowledge of God. What God foreknows must, in the very nature of the case, be as fixed and certain as what is foreordained; and if one is inconsistent with the free agency of man, the other is also. Foreordination renders the events certain, while foreknowledge presupposes that they are certain.
Now if future events are foreknown to God, they cannot by any possibility take a turn contrary to His knowledge. If the course of future events is foreknown, history will follow that course as definitely as a locomotive follows the rails from New York to Chicago. The Arminian doctrine, in rejecting foreordination, rejects the theistic basis for foreknowledge. Common sense tells us that no event can be foreknown unless by some means, either physical or mental, it has been predetermined. Our choice as to what determines the certainty of future events narrows down to two alternatives — the foreordination of the wise and merciful heavenly Father, or the working of blind, physical fate.
When the Arminian is confronted with the argument from the foreknowledge of God, he has to admit the certainty or fixity of future events. Yet when dealing with the problem of free agency he wishes to maintain that the acts of free agents are uncertain and ultimately dependent on the choice of the person,—which is plainly an inconsistent position. A view which holds that the free acts of men are uncertain, sacrifices the sovereignty of God in order to preserve the freedom of men.
Furthermore, if the acts of free agents are in themselves uncertain, God must then wait until the event has had its issue before making His plans. In trying to convert a soul, then He would be conceived of as working in the same manner that Napoleon is said to have gone into battle-with three or four plans in mind, so that if the first failed, he could fall back upon the second, and if that failed, then the third, and so on, —a view which is altogether inconsistent with a true view of His nature. He would then be ignorant of much of the future and would daily be gaining vast stores of knowledge. His government of the world also, in that case, would be very uncertain and changeable, dependent as it would be on the unforeseen conduct of men.
To deny God the perfections of foreknowledge and immutability is to represent Him as a disappointed and unhappy being who is often checkmated and defeated by His creatures. But who can really believe that in the presence of man the Great Jehovah must sit waiting, inquiring, "What will he do?" Yet unless Arminianism denies the foreknowledge of God, it stands defenseless before the logical consistency of Calvinism; for foreknowledge implies certainty and certainty implies foreordination.
What is the Apostolic argument against this?
Here's a great one by Arthu Pink...
THE FOREKNOWLEDGE OF GOD
"...It thus appears that it is highly important for us to have clear and spiritual views of the “foreknowledge” of God. Erroneous conceptions about it lead inevitably to thoughts most dishonouring to Him. The popular idea of Divine foreknowledge is altogether inadequate. God not only knew the end from the beginning, but He planned, fixed, predestinated everything from the beginning. And, as cause stands to effect, so God’s purpose is the ground of His prescience. If then the reader be a real Christian, he is so because God chose him in Christ before the foundation of the world (Eph 1:4), and chose not because He foresaw you would believe, but chose simply because it pleased Him to choose; chose you notwithstanding your natural unbelief. This being so, all the glory and praise belongs alone to Him. You have no ground for taking any credit to yourself. You have “believed through grace” (Acts 18:27), and that, because your very election was “of grace” (Rom 11:5)."
And here's Warfield's terrific essay...
SOME THOUGHTS ON THE PREDESTINATION OF GOD
"...To say Predestination is to say all this. It is to introduce order into the universe. It is to assign an end and a worthy end to it. It enables us to speak of a far off divine event to which the whole creation is moving. It enables us to see that whatever occurs, great or small, has a place to fill in this universal teleology; and thus has significance given it, and a juustification supplied to it. To say Predestination is thus not only to say God; it is also to say Theodicy. No matter what we may say of Predestination in moments of puzzlement, as we stand in face of the problems of life—the problem of the petty, the problem of suffering, the problem of sin—it is safe to say that at the bottom of our minds we all believe in it. We cannot help believing in it—if we believe in God; and that, in its utmost extension, as applying to everything about us which comes to pass..."