The doctrine of election is easier to understand than it is to stomach. God has chosen from eternity past those who will enter heaven (Acts 13.48; Eph 1.3-6). To state it negatively, no one will enter heaven who has not been chosen from eternity (Jn 10.26). These are simple enough statements, on which both Calvinists and Arminians agree, but are convictions hard to come by.
Arminians and Calvinists love Scripture and hope to embrace what Scripture teaches. Therefore, both agree that the "elect" (i.e. chosen, children of God, church, saints) are the only ones going to heaven (2 Tim 2.10). They must also agree that the basis on which God elects (or predestines, chooses, etc.) them is foreknowledge (Rom 8.29).
Examine Rom 8.29-30 in reverse order. Those glorifed are only those justified. Those justified are only those called (effectually to salvation). Those called are only those predestined (to salvation). Those predestined are only those foreknown to that end. In other words, those foreknown consists of the same number as those glorified. God glorifies in the end the same folks he foreknew in the beginning.
A critical hinge, therefore, is how we understand foreknowledge. Calvinsists define foreknowledge essentially as foreloving. Foreknowledge is not mere "prior knowledge" but prior affection. The common example is Gen 4.1, where Adam "knew" Eve. He didn't come into some facts about Eve, but engaged her intimately and affectionately.
Jesus will one day say to some who were confident in their self-righteousness, "I never knew you" (Mt 7.23). He didn't mean he didn't know the fact of their existence, but that he didn't have a familial, loving relationship with them. Therefore, Calvinists consider foreknowledge God's prior affection set on those he will then predestine, call, justify and glorify. His saving acts are based on no other reason other than God chose to love them before the foundation of the world. Hence, we derive the term "unconditional election."
Arminians object that this understanding of foreknowledge charges God with duplicity. How can God honestly demand everyone repent and believe when he's determined that some don't? He would be like Lucy who promises Charlie Brown she'll keep the football steady, but who always jerks it away at the last minute. For God to be truly and freely worshiped he must allow all men to truly and freely chose him before he acts savingly on them.
The foreknowledge, therefore, on which God's election is based (something Scripture clearly teaches and on which Calvinists and Arminians agree) cannot be foreloving, but foreseeing. In eternity past and according to his omniscience, God could see those who would freely choose him (i.e. exercise prevenient grace) in their lifetimes. And because they would choose him he then elected or predestined them to salvation, a gracious act God was not obliged to do. Hence, we derive the term "conditional election," with the condition being foreseen faith.
This definition begs as many questions as the Calvinist definition. For example, (1) Does it hold true in texts like Acts 2.23, Rom 11.2 or 1 Pt 1.20? This post is long enough without explaining that it doesn't. (2) If saving faith is God's gift (Eph 2.8-9), then isn't whatever faith God foresees merely what he must give those who believe? In essence, God foresess that he will grant saving faith to some and not others (and we're back to square 1!).
At any rate, this definition of foreknowledge apparently relieves God of any charge of unfairness, and encourages true and free (uncoerced) responses to the gospel. However, I submit that such a definition in no way leaves God off the hook, but still demands that God explain himself as it were. Let me offer a philosophical defense of this thesis.
For the sake of argument, I'll grant the Arminian definition of foreknowledge: God simply knew beforehand (by his omniscience) those who would respond savingly to the gospel and on that basis elected them to salvation. If God eternally knew who would believe, did God not also - by that same omniscience - know those would not respond savingly to the gospel? In other words, God must've known those who would not believe as surely as he knew those who would. And knowing that, God still chose to create those he knew would not believe.
The Arminian must still explain why God would create those he knew beforehand would go to hell. God is still on the hook and must explain himself because he hasn't been relieved of apparent "unfairness."
Some possible explanations are: (1) God's omniscience is not comprehensive or reliable. Some of those he foresaw as believers turn out not to be, or vice versa. What he thought to be true in eternity past turns out not be in time and history. In order to be "fair," God has to allow that some fall through the cracks or pleasantly surprise him. Simply stated, one must allow that God could be wrong about some of those he foresaw in either condition.
(2) God grants prevenient grace to all those he creates, even those he knows will not believe in hopes that they might. Then we're left in the same predicament as the Calvinists: God cannot genuinely demand repentance and faith from those he already knows will not do so. Unless, of course, God might be wrong about someone in the end and he's hedged his bets by granting prevenient grace. This doesn't seem consistent with Rom 9.17-18, 22-24.
(3) For God to be "fair," he must create only those he's reasonably hopeful will believe the gospel. Otherwise, if he creates someone he knows will not do so (based on his omniscient prior knowledge) he's not fair because that person doesn't have a real "shot" at salvation (unless (1) is true). But, in what sense can Judas then be called the "son of perdition" (Jn 17.12) or anyone a "vessel of wrath prepared for destruction" (Rom 9.22)?
Judas was such because he chose to be and God honored his choice. I can summarily agree with that. But the fact remains that God created Judas (fore)knowing he would not believe. In fact, he created Judas (a devil, Jn 6.70) to be the agent of Jesus' arrest and, with the rest, his executioners (Acts 2.22-23; 4.28). Otherwise, how could God guarantee that Jesus would even be killed? And if there was no guarantee that Jesus be killed then there has been no authoritative promise of salvation.
The Calvinist understanding of foreknowledge makes better sense of the biblical witness. Whatever God foresaw in me, it was not love for him (1 Jn 4.10, 19) but rebellion against him (Rom 5.8, 10). And although Arminians want to honestly relieve God of any guilty charges, they leave me with more questions about his omniscience and omnipotence. I'm thankful that God didn't foresee me, but foreloved me "to the praise of the glory of his grace" (Eph 1.6).