However, according to Christianity, the purpose of the universe is not to be morally or physically perfect, but to provide a place where spiritual creatures can choose to love or reject God - to live with Him forever in a new, perfect universe, or reject Him and live apart from Him for eternity. It would not be possible to make this choice in a universe in which all moral choices are restricted to only good choices. Einstein didn't seem to understand that one could not choose between good and bad if bad did not exist. It's amazing that such a brilliant man could not understand such a simple logical principle.
That's not quite right.
God did not put us in this universe in order to choose between good and bad. He put us in this universe so that we might grow. We were never meant to choose evil, evil was never meant to be part of this universe.
God created everything.
God created everything good.
Evil is, therefore, not a created thing - it is a distortion or twisting of the good, an absence of the good.
Evil does not have its own existence because God didn't create it and nothing else has the power to bring existence out of nothing. Thus evil cannot have its own existence. At best, it is something that is less good than it should be, sometimes radically less good. Evil is that which lacks the good it should have.
In short, evil is illusion, it is the illusion that something exists where nothing actually exists.
That's why Aquinas said the doing of evil is the choice of the good instead of the best. When we mistake the good for the best, when we choose the good instead of the best because we have confused the two, we have committed evil. When we confuse ourselves deliberately, we commit sin.
To say that God created the universe so that we had to choose implies that evil MUST exist alongside good.
This is the heresy of the Manichees: the idea that evil is necessary to the universe.
The purpose of the universe is, indeed, to be morally, physically perfect, but that perfection is something we are meant to attain through growth in our knowledge and understanding of God. As we grow in our intimacy with God, we are supposed to train creation to attune itself more and more towards God.
Our knowledge of God is supposed to make our faith, our trust in Him, grow, mature, become unshakeable. We do not grow through choice, we grow through delving ever deeper into intimate communion with the Persons of God.
It isn't choosing the good over the best, but choosing the best over and over again, and learning something new each time we do it - that is what we were originally meant to do.
It is what we are still meant to do.
In heaven, we cannot choose evil.
But that is not because evil doesn't exist, rather it is because our knowledge, our understanding, our communion with God has expanded to such an enormous degree that it overflows the full capacity of who we are.
In heaven, I have such an enormous understanding of God's goodness, it is so immediate, so pure, so powerful, that there is no more room for the illusion that anything else approaches His goodness.
I can't choose evil anymore because there is no room in me to be fooled anymore. My growth is complete, my knowledge has reached its zenith, my understanding has reached its depth, my intimacy has reached its perfection.
It isn't about choice.
It never has been.