Introduction. One of the most famous objections to the existence of God is that the joint claims that God is morally perfect and omnipotent are incompatible with the existence of evil and suffering. For if God were all good, the argument goes, he would want to prevent evil and suffering; and if he were all powerful, he would be able to do so. Therefore evil and suffering prove one of three things: That God does not exist, or that he is not all good, or that he is not all powerful. In short: The existence of an all-loving and all-powerful God is improbable given the obvious general fact of human suffering.
Definition of Terms. Before responding, I need to briefly define a few terms that will be of use in what follows. “Free will” is the power of an agent to perform actions that are influenced but never fully determined by forces external to himself but of itself free will does not necessarily entail the capacity to do evil. God could, for instance, give us free will but constrain its exercise to the choice between different but equally good actions. I will therefore use the term “moral liberty” for the power of an agent to exercise his free will in making choices between good and bad actions; and “moral evil” for the use of moral liberty to perform bad actions. Finally, I will use the term “natural evil” for suffering having causes unrelated to moral evil—the suffering caused by natural disasters, accidents, diseases, and so on.
1. Moral Evil. To see why the problem of evil fails to disprove theism we first need to understand omnipotence in a more careful way. Theologians have always understood omnipotence to mean the power to perform any logically possible action. To note that God could not create a square circle imposes no limit on his powers because creating a square circle is not an action whose difficulty lies in the brute force required to perform it. In fact, it is not an action at all; rather, the imperative Create a square circle is a logically incoherent combination of English words which have no referent in the set of all logically possible actions that belong to omnipotence.
The relevance of this point to moral evil should be immediately obvious. It is logically impossible for God to create agents with moral liberty and ensure that they do not sin. The potential for moral evil is therefore an unavoidable consequence of moral liberty. The question that needs to be asked is whether moral liberty confers any significant benefits upon mankind; and if it does, whether those benefits outweigh the suffering that it entails. In the following paragraphs I will be arguing that it confers upon mankind very significant benefits indeed; namely, that it makes possible the attainment of virtue, the formation of moral character and the capacity for genuine love.
1.1 The Attainment of Virtue. To understand the importance of moral liberty to virtue, imagine a world from which moral liberty has been removed; in other words, a world in which the only possible exercise of free will is in the choice between different kinds of equally good actions. The result would be a toy universe or pleasure park in which we exist like animals or small children—experiencing comfort and sensory pleasure but without the opportunity to show empathy, courage, patience, self-sacrifice, forgiveness or heroism. Such thought experiments help to bring out an important moral distinction between innocence and virtue. Innocence is a mere ignorance of evil; virtue requires that one face a significant choice between good and evil and freely choose the good. And since it is logically impossible for God to force us to freely choose the good, any world in which virtue is attainable is a world in which moral evil is a distinct possibility.
1.2 The Formation of Moral Character. Because we have moral liberty we are continuously faced with the choice between performing good and bad actions. And, as Swinburne notes, humans are so made that when we choose to do good, it becomes slightly easier to choose to do good again at the next opportunity; and when we choose to do evil, it becomes slightly easier to choose to do evil again at the next opportunity. In this way, over time, we are able to change the desires that influence us and form either a very good or a very bad character. Without moral liberty our characters would have and unwaveringly maintain whatever measure of good or evil God elected at our creation and would therefore be completely devoid of moral significance.
1.3 The Capacity for Genuine Love. Love that is induced through the use of potions, hypnotism or spells is not considered genuine. For love between humans to be genuine, it must be freely given. It follows from this simple truth that any world in which genuine human love is a possibility is a world in which moral evil is a possibility. And this is because if you are truly free to give love you must be truly free to withhold it—even in situations where withholding it would be wrong. For a mother’s love for her young children to be genuine, for example, it cannot be forced upon her from above by God; it must be freely given and in that case it must be logically possible for her to withhold it—and so, perhaps, to neglect and abuse her children. All this holds equally for our love of God. To be genuine a love of God cannot be built into us by God. It must be freely given and this entails the freedom to withhold it.
Moral liberty therefore confers the profoundest imaginable benefits upon mankind. It provides us with the opportunity to attain virtue, form a moral character, and experience genuine love for each other and for God. It is not at all incoherent to suppose that a perfectly good person would choose to create a world in which these supreme goods were possible—even at the cost of moral evil.
2. Natural Evil. In discussing natural evil it is important to recognise that the suffering it entails is often bound up with moral evil. Cheaply built and poorly planned towns, for instance, can significantly raise the death toll during earthquakes and floods; the misuse of certain chemicals can significantly increase the incidence of cancer; the failure of wealthy countries to provide aid to poor countries can result in preventable famines—and so forth. Nevertheless, there is a great deal of suffering on Earth for which no human agent is responsible. And in what follows I will be arguing that such natural evil fulfils three additional and important purposes which moral evil alone could not fulfil: It ensures that opportunities to obtain virtue are universal; it broadens the scope and significance of our moral choices; and, most importantly, it conduces to the religious life.
2.1 It Makes Opportunities to Obtain Virtue Universal. In the section discussing moral liberty, we saw that empathy, courage, patience, self-sacrifice, forgiveness and heroism are all states contributive to virtue. But it needs to be noted that it is not moral liberty alone, but moral liberty and moral evil together, that provide an opportunity to manifest these virtues. In other words, only if someone eventually exercises their moral liberty to assault or abuse you can I exercise mine to show you empathy; only if you are robbed can I make personal sacrifices to provide for you. The question arises whether moral evil alone would afford adequate opportunities for everyone to form a virtuous moral character. In this connection Swinburne writes,
You can show courage when threatened by a gunman as well as when threatened by cancer; and show sympathy to those likely to be killed by gunmen as well as to those likely to die of cancer. But just imagine all the suffering of mind and body caused by disease, earthquake, and accident unpreventable by humans removed at a stroke from our society—no sickness, no senility, no bereavement in consequence of the untimely death of the young. Many of us would then have such an easy life that we simply would not have much opportunity to show courage or, indeed, manifest much in the way of great goodness at all.
Consider a world without disaster, disease and decrepitude; a world in which the only cause of injury and death is, respectively, assault and murder. It is a mathematical certainty that such a world would provide far, far fewer opportunities for virtue and highly probable that some people would have no such opportunities at all.
2.2 It Broadens The Scope of Moral Liberty. Moreover, with careful reflection it is apparent that the removal of natural evil would also considerably constrain the scope and significance of moral liberty. For instance: The knowledge that poison causes death is unobtainable unless someone is first observed to have accidentally died by poisoning. And knowledge of poisonous toadstools and berries thereafter affords us an opportunity to exercise significant moral liberty: We can use that knowledge to kill off a neighbouring village by poisoning its well or to warn the neighbouring village not to eat toadstools. Earthquake belts, to give another example, give us a choice between building upon them cities that may be destroyed long after we are dead or avoiding doing so. Pathogens give us a choice between making biological weapons that kill thousands or developing antibiotics that save thousands. These examples show that natural evil broadens the scope and significance of our choices so that they are able to benefit or harm others far from us in both time and space. This confers on us a solemn moral responsibility and significance and so plausibly conduces to the aims of a morally perfect creator for his creatures.
2.3 It Conduces to the Religious Life. If God exists he is the consummation and source of all power, knowledge, wisdom, beauty, rationality and love lying at the very heart of reality. A genuine and eternal love relationship with God is therefore the greatest conceivable good available to us. The question arises: Does a world that contains moral and natural evil conduce to the greatest number of creatures freely seeking the greatest conceivable good available to them? Reason and experience suggest that the answer may be yes. Pleasure and comfort are good and our world, of course, provides both. But a life that offered nothing else would make us complacent, hedonistic, idle and shallow. Suffering and death, on the other hand, force us all to confront questions about the ultimate meaning of life and so, for very many, plays a causal role in developing a relationship with God and living a religious life.
Conclusion. The objection from evil seems ultimately to rest on the naive assumption that God created the universe to serve as a comfortable habitat for his human pets. However, we have seen that moral and natural evil are an unpreventable feature of any world in which the supreme goods of virtue, moral self-determination, genuine love and knowledge of God are significantly and universally attainable. It is probable that the creation of a pleasure park inhabited by creatures who know endless pleasure and comfort but are devoid of moral and spiritual significance would be a morally good act. But it is not at all incoherent to suppose that, viewed under the aspect of his infinite intelligence and moral perfection, God would know that the creation of a world precisely like ours is a morally better act. This is the so-called “Higher-Order Goods” solution to the problem of evil. Pleasure, innocence and comfort are good; but virtue, moral significance and love are goods of a higher order. And God, being perfectly good, wants to give us the very best things He has to give.
 To create agents with moral liberty and constrain them from moral evil is simply to deny them moral liberty. It is logically possible, though hugely improbable, that a planet of agents with moral liberty will by chance alone contain no evil. But, needless to say, this state of affairs does not obtain on our planet
 The question arises whether God can freely withhold his love and if not then how, given my argument, it can be genuine. However, the difficulty only arises in the case of finite persons created by God for the purpose of knowing and loving him and each other. For if God created us with an immutable and irresistible love for himself and each other, that love would have its origin in something external to ourselves—namely, God—and would not therefore be freely given and genuine. But since God’s love is past eternal and has no cause external to himself, it is genuine even though by a necessity of his divine nature he is incapable of withholding it.