Arminians typically define freewill as the freedom to do otherwise. More recently, this has been cashed out as the principle of alternate possibilities.
They sometimes try to give this metaphysical grounding in the nature of God. They claim that God has libertarian freedom, and since we’re made in God’s image, we share that attribute.
Some Arminians also believe in the perseverance of the saints. They appeal to the fact that the Remonstrants left this question open.
There are also some Arminianism who subscribe to postmortem evangelism.
By way of reply, Calvinists raise some stock objections to their position. We ask them if God can sin. Can God choose between good and evil? We also ask them in the saints in glory can sin. Can they lose their place in heaven?
In response, Arminians say the freedom to do otherwise doesn’t require both good and evil choices. As long as there is more than one good choice, you have alternate possibilities to choose from.
And that’s true. It’s also a good way to gloss God’s freedom.
However, while that’s a valid distinction in its own right, it creates fundamental problems for Arminianism. To begin with, it’s ad hoc to say that we have libertarian freedom because God has libertarian freedom, but then, when asked whether God can sin, introduce a major discontinuity between human freedom, which includes the freedom to sin, and divine freedom, which excludes the freedom to sin. Either God is the template for human freedom or he’s not.
And, if anything, there’s a deeper objection. The freewill defense is the Arminian theodicy of choice. This is how Arminians explain the possibility of sin. And this is how Arminians justify the divine permission of evil.
God couldn’t make men who only do right without infringing on their freedom of choice. “True” loved can’t be “forced.”
Although it’s possible for God to make men who only do right, they would be “robots” and “puppets.”
But if, in reply to our objections, Arminians concede that the freedom to do otherwise only requires alternate goods, then they abandon the key presupposition of the freewill defense. For the freewill defense is only compelling if there’s no possible world where human beings freely and invariably do good.