The problem of evil is one of the oldest and most emotionally powerful arguments for atheism. It’s usually formulated in the following way: 1. God must be all-powerful, all-knowing, and all-good. 2. An all-powerful, all-knowing, and all-good being would eliminate evil. 3. Evil exists. 4. Therefore, God does not exist. Although this argument is emotionally powerful, from a logical perspective it suffers from a glaring weakness. Specifically, it leaves out a key premise that is usually never argued for: “God can have no good reason to allow evil to exist.” But St. Thomas Aquinas said that “God allows evils to happen in order to bring a greater good therefrom.”1It’s important to understand that evil is not created by God. Instead, evil is an absence of good that God tolerates because through it can come a good that he did create. There are two types of evil—moral evil and natural evil. A moral evil occurs when an agent acts against the good, such as a man poisoning his wife so he can marry another woman. Natural evil, on the other hand, occurs when bad effects follow from a morally good or non-moral cause, such as a woman accidentally drinking poison and dying. Moral evils are privations of the good and represent a defect in the one who is causing the moral evil. God cannot directly create these evils as he has no defects, but he can directly create physical suffering. That’s because natural maladies, like pain, can ultimately serve God’s good ends and are not inherently evil. Therefore, if God has morally sufficient reason to allow evil or suffering, then what is called the argument from evil for atheism falls apart, because God and the existence of evil are not logically contradictory. So what reasons might God have for allowing evil to exist? One reason might be the goal of creating creatures who freely choose the good and avoid evil. If God always compelled human beings to choose the good then our actions would be morally insignificant. They would be no different from the preprogrammed actions of appliances or robots. But if God allows human beings to choose to love, or to choose the good, then it is possible that some humans may choose evil instead. Thus, some critics might object that if I make a robot that I know will malfunction and hurt other people, then I am responsible for what the robot does. Since God made us and knew we would sin, this makes him responsible for the evil we do. But the problem with this objection is that the robot doesn’t choose to harm anyone; if it harms someone, it’s just following its programming. In that case, we rightly blame the programmer. But human beings aren’t robots programmed by God; when they freely choose to do evil we can’t blame God for it. But what about natural evils like disease or disasters? Free will may not explain why God allows these evils, but there may be other reasons why God allows them to exist. First, in a limited, physical world like ours there will always be competing goods that result in natural evils. For example, as fire burns, it consumes the oxygen around it. When a lion eats a zebra and becomes more perfect it reduces the goodness found in the zebra.