The strongest argument against the existence of God and Aquinas's answer
I am a Christian, but I'm also a scientist and a philosopher. If my beliefs are true, therefore, I believe they ought to stand up to scrutiny.
All arguments against the existence of God, and by God I mean the God of the Bible, all good, all knowing, all powerful, tend to call God's existence into question but are not direct proofs against His existence.
For example, the argument from lack of evidence calls God's existence into question, but absence of evidence is not evidence of absence. One can simply say that God chooses to reveal Himself according to His own designs.
There is one argument, however, that is a direct counterproof of the existence of the Christian God. It is, in fact, the one that probably creates the most Atheists who could, otherwise, easily handle a lack of evidence.
It is the Argument from Evil.
The well-known argument simply goes like this (copied from The Problem of Evil, Stanford Encyclopedia of Philosophy)
If God exists, then God is omnipotent, omniscient, and morally perfect.
If God is omnipotent, then God has the power to eliminate all evil.
If God is omniscient, then God knows when evil exists.
If God is morally perfect, then God has the desire to eliminate all evil.
Evil exists.
If evil exists and God exists, then either God doesn’t have the power to eliminate all evil, or doesn’t know when evil exists, or doesn’t have the desire to eliminate all evil.
Therefore, God doesn’t exist.
The proof seems ironclad, but you can question any of the premises or the logic and see where it takes you. For example, you can say that God is not omnipotent, not omniscient, or not morally perfect, but the Bible as well as Christian teaching and tradition is very clear that God is all of these.
It is hard to call #5 into question. Moral relativists say that evil is a cultural byproduct. Buddhists suggest it is impossible to ascribe evil to any action or event because good and evil events are interconnected. But most people believe evil exists and if you are trying to show the God of the Bible exists you can’t deny it.
You can call into question #6. You could say that God can have the power, know about, and have the desire to eliminate evil and still exist.
You can take the perspective that God started the world in a morally perfect way but by giving human beings free will we enabled evil to enter the world.
The Book of Job suggests that evil done to us is part of a higher plan or purpose. In that case, Job suffers greatly despite having done nothing wrong. Why? Job is told that God's plans are too mysterious for him to understand. But the reader is given more information. We are told it is because God wanted to protect Job's reputation before Satan. (If you don't believe me, go read it.) Thus, God believed it was a higher moral good to protect Job's reputation before the Devil than to prevent his suffering.
I don't know about you, but I find this hard to swallow. Job is an ancient story and I sometimes think something important was lost there.
The Christian perspective is not the one of the Book of Job. It is this: God sent his only Son to die on a cross in order to rescue those who believe in him from evil, for it is in that death and resurrection that a fatal blow is dealt to the powers of evil who seek to condemn and accuse human beings.
Yet, that says little about why evil was allowed in the first place. Some argue that God could not be morally perfect if he did not first allow evil to exist. For, vanquishing evil is more morally perfect than not allowing it to exist in the first place. This is slightly different than the free will argument. It means that God purposefully allowed evil to exist in order to destroy it.
There is some Biblical support for the idea. For example there is Isaiah 45:7 which says,
"I form the light, and create darkness: I make peace, and create evil: I the LORD do all these things"
There is also Amos 3:6,
"Shall there be evil in a city, which the Lord hath not done?"
The book of the Apocrypha, 2 Esdras 4:30 is probably the closest to making the admission that God authored evil:
"For a grain of evil seed was sown in Adam’s heart from the beginning, and how much ungodliness it has produced until now—and will produce until the time of threshing comes!"
This suggests that God purposefully made Adam evil so that Christ could come and overcome it.
I think many of us, when we or a loved one suffers because of evil, would say, "maybe you could be a little less perfect, then, God, a little less sovereign?"
Thomas Aquinas, characteristically, took the problem of evil head on and his answer, contained in Summa Theologica 1:49, is much more subtle than this. His answer is to refute the statement #4 above. In other words, a morally perfect God does not seek to eliminate all evil.
Aquinas defines evil as a lack of good but believed that all things that have existence are in themselves good. Therefore, nothing that God has created is intrinsically evil.
Evil arises rather from some defect in action or deprivation of something. That is, a thing, which is itself good, acts in a way that is defective or improper or deprives a person of some needed thing.
For example, all people, according to Aquinas are good, but through an ill will a person can do evil by taking actions that are morally improper or defective.
On the question of whether God is the cause of evil, Aquinas answers that God is responsible for only "just" evil. Thus, in the passages from Isaiah and Amos, God is rendering "evil" to those who rebel against him and do evil themselves. For unjust evil, God is not the cause because God has no defect in him that would allow for evil. Rather, God has created a universe such that justice can be done and such a universe must, therefore, allow for people to do evil as well.
You can think of this in terms of a justice system that enables murderers to be put into prison. It must also allow people to be unjustly imprisoned. Or that a person can shoot someone in self-defense and be morally justified but also shoot someone to rob them. God allows people the free will to determine moral actions from immoral ones and to enact justice on one another for good but also enact injustice on one another by those same actions applied improperly.
Free will, in fact, doesn't have a lot to do with the existence of evil, in Aquinas's argument, unless you think that inanimate matter has free will too. For, the possibility of defect in action can apply to things as well as people when they cause people to suffer. The world allows for all sorts of things to happen, not to allow us to have free will, but because God's will requires those things to be possible for good.
What about evil people or bad things happening like illnesses? Why allow those things? Did God invent cancer as some punishment?
Aquinas answers that defects cannot be caused by God. This is because defects are the result of bad action. So, for example, cancer is the result of cells, which are in themselves good, doing what they are supposed to do, dividing, but doing it improperly. Thus, the existence of cells and their ability to divide is caused by God, but their doing it improperly is not. It is a defect in their action. This is despite their having no free will.
Thus, if a person is evil, it is because of a defect in their moral character, but not a defect in the person's being. That is on them, not on God. God may have given a person the potential to do great things, but they squandered it doing evil. This is the meaning of 2 Esdras. Adam, not God, sowed the evil into his heart.
If something bad happens to a person, but no one was at fault, Aquinas considers that to be evil as well, because it deprives somebody of good. Fire is good and keeps us warm but if your house burns down that is bad because it deprives you of shelter and your possessions. The problem isn't fire itself, but the defective action of the fire. This is true of all natural, physical phenomena. They are in themselves good, but bad things can come from them.
From Aquinas's perspective, even great evil lies with squandered potential and defective moral character in human beings or in accidentally defective action in natural things, not in God.
We can ask where was God during the Holocaust, but the blame lies squarely with the evil will of those involved. Aquinas would not argue that it was part of a master plan. He would say that we live in a universe that allows people to be imprisoned, starved, tortured, and killed and that it is up to us human beings to make sure that doesn't happen.