J. L. Mackie, in his famous essay "Evil and Omnipotence," believes he has refuted the free will defense (FWD) of the problem of evil. FWD states, according to Mackie, that "evil is due to human free will."
Mackie asks this question: "If God has made men such that in their free choices they sometimes prefer what is good and sometimes what is evil, why could he not have made men such that they always choose the good? If there is no logical impossibility in a man's freely choosing the good on one, or several, occasions, there cannot be a logical impossibility in his freely choosing the good on every occasion. God was not, then, faced with a choice between making innocent automata and making beings who, in acting freely, would sometimes go wrong: there was open to him the obvious better possibility of making beings who would act freely but always go right. Clearly, his failure to avail himself of this possibility is inconsistent with his being both omnipotent and wholly good."
Here's why I think Mackie's point fails. The choice to love requires the choice to not love. God is a being whose essence is love. God is a relational being, and desires relationship with his created beings. God wants persons to love him, as he loves them. Only if there is a possibility to choose to not-love can love be meaningful. Note also that "love" cannot be fully explicated by "logic." And "relationship" cannot be so explicated either. Mackie's "logic-only" hermeneutical tool cannot make sense of either love or relationships.
But now a question might arise: If loving requires a choice between to love or not to love, then how will this apply in heaven? On the Christian view of heaven surely there will be no evil or "non-love" towards God. If love requires making a choice between good and evil then how can we be said to love God in heaven? I think the answer to this is as follows. On earth we make the choice to either love God or not love God. In heaven we will have eternal relationship with the One we have chosen to love. In heaven the personal presence of God will be so infinitely overwhelming that it will be relationally impossible to choose not to love God.
Here's a simple analogy to explain this. We can imagine that there exists at least one person who, if a guarantee of perfect health for himself and all his loved ones were freely offered to him with no strings attached, that he would take it. Of course because he has free will he could choose to not take this offer. But we can imagine this particular person to be so overwhelmed with this offer and so filled with grtitude that, even though he could refuse, he will not refuse.
Now, multiply this example by infinity, and one can see how in heaven, even though we will have free will and could choose to not love God, such a choice will be relationally impossible and will not happen.
This right raise another question: why then does God not reveal himself to us in such a way here on earth that we will freely choose to love him? The answer to that is: such an act on God's part would be too coercive, and for all practical purposes take away our relational free will.