"With every advance in our thought the unity of the creative act, and the impossibility of tinkering with the creation as though this or that element of it could have been removed, will become more apparent."
—C.S. Lewis, The Problem of Pain
In the above quote, C.S. Lewis argued that even an infinitely powerful deity could not have created a world entirely without evil or suffering, and that whatever evil or suffering does exist must be an intrinsic part of creating any world at all, and therefore not something for which we can rightfully blame God. Similarly, the philosopher Gottfried Leibniz claimed that, since God was benevolent and omnipotent, this must necessarily be the best of all possible worlds.
A look around at the world we actually live in, however, should convince any rational person that these claims of Panglossian optimism are born from believers' preexisting apologetic desire to defend their faith, not from any passing acquaintance with the evidence. This world is not the best of all possible worlds, not by a long shot, and there are many ways in which it could have been improved had it been created by a wise, benevolent and powerful deity. Since we would expect goodness, harmony and happiness to be the norm if the world had been created by such a being, whereas in reality we see vast amounts of disharmony, evil and suffering, it is all but certain that the world was not created by such a being. In this essay, I will imagine some ways in which this world could have been improved, things we might have expected to see if our existence had been created by a loving divinity.
In the Christian conception, God is omnipotent. He is not bound by physical laws, but can freely alter those laws to his liking. The only limit which applies to God is the limit of logical possibility: God cannot do what is logically impossible, for example, create a world where there both is and is not evil. Other than this trivial restriction, God can create literally any self-consistent world which it is possible to imagine. In this essay, I will take this conception as a model. Claims that God lacks the power to create a world better than our own will not be considered here, since that is not the position taken by the vast majority of believers.
First, the most obvious response to Lewis' claim is that humans have already removed several elements of the world which we found uncongenial. For example, smallpox has been eradicated completely and no longer exists in the wild at all. Numerous other diseases, such as polio, have been almost completely wiped out or at the very least brought under control through vaccination and other medical advances, so that millions of people can live lives free of the fear and suffering they cause. If this task is possible for mere humans, then it must be possible for a far more powerful supernatural being. As our efforts at vaccination and medical care show, there is no intrinsic reason why our world requires the existence of tuberculosis, bubonic plague, AIDS, or any of the other infectious diseases that bedevil us. If God exists, he would not have allowed such plagues to come into existence in the first place.
To those theists who would respond that eliminating disease and other checks on human population would cause our numbers to grow out of control and cause even more people to suffer and starve, I point out that God could have made human beings so that our natural drive is not to reproduce continually regardless of the environment's ability to support them, but so the population increases only up to a sustainable level and then ceases to grow any further. Even in our world, some species have abilities like this: some bacteria, for example, have a genetic mechanism called "quorum sensing", which enables them to alter their behavior based on how crowded their environment is. God could have installed a more sophisticated version of this sense in human beings, causing either the desire to have more children or the physical ability to do so to decrease in proportion to how many of us there are.
In fact, God could have put such a sense not just in humans, but in all living things. Such a change would have improved the world by putting an end to the Malthusian struggle that currently obtains, where every species seeks to multiply as much as possible and is kept in check only by starvation, disease, parasitism, predation and other means of death. This natural order ensures vast amounts of constant struggle and bloodshed among living things, and what's more, ensures that the scythe always falls most heavily on the innocent young - both human and otherwise. A wise god could have framed the natural order differently so as to exclude this outcome.
Talking of the Malthusian struggle to reproduce, there is another area where improvements could have been made. Giving birth, for human beings, is a horrifically painful and risky affair. The large heads that give us room to be intelligent, and the narrow pelvises that allow us to walk upright, are two highly beneficial adaptations taken separately, but put together, they mean that giving birth is vastly more difficult and dangerous for human women than it is for any other mammal. A blind process such as evolution cannot be blamed for becoming trapped in this cul-de-sac of adaptation, but a foresightful intelligent designer could surely have come up with a better solution. Why not give human mothers a pouch like marsupials, so that a fetus could finish developing in safety outside the mother's womb?
I have another, related suggestion. Christian conservatives often rail against divorce, promiscuity, masturbation, extramarital sex, and other forms of sexual interaction that fall outside their preferred model of total abstinence followed by lifelong monogamy. Yet the very strength of the human sex drive makes that model extremely unrealistic and unattainable for all except a few. If monogamy is what God wants, I have a better idea: create a world where the ritual of marriage induces physiological changes in a person that cause them to forever after feel sexual and romantic attraction only towards their mate, and not toward anyone else. Such a change would eliminate at one stroke most of the social ills pointed to by religious conservatives. If God wanted us to abstain from such behaviors, he could have created us so as to naturally exclude them, rather than creating people with extremely strong inclinations to do the opposite of what he wants them to do, and then becoming furious at and harshly punishing those people who give in to those inclinations.
Likewise, if God is so angered by people hurting other people, there would be an easy way to drastically decrease the occurrence of that. Although human beings already have a decent sense of empathy, he could have given us a much stronger one, something like the emotional telepathy often found in science fiction. With this sense, which there would be no way to block, you would perceive all the emotions of people around you: not just to understand what it would be like, but to actually feel them yourself. Any fear that you induced in another person, any pain you caused them, you would feel as if it were your own. In the vast majority of cases, I am sure, this would so appall the offender that they would be unable to do what they had intended.
There are many more ways to improve this world I could think of that I haven't listed here. Perhaps some readers will disagree with some of my specific suggestions, which is fine. However, I challenge any theist readers who believe in an omnipotent and benevolent god to tell me that they cannot think of one single way in which this world could have been improved upon. I'd wager that honesty would compel them to admit otherwise.