A Simple Argument Against Naturalism
If naturalism is true, then everything that exists is composed of matter and energy. There is no God and no immaterial soul. Everything that you think or feel results from the arrangement of the atoms in your brain.
Furthermore, if evolution is also true, then these physical structures in your brain came into existence through the mechanism of natural selection weeding out random genetic mutations. Therefore enduring human beliefs and feelings came into existence only because, at some point in time, these beliefs and feelings promoted the survival of the human species.
Therefore, assuming both naturalism and evolution are true, the universal human impulse of love came into existence because this instinct enabled humans to live together in peaceful societies, pooling their knowledge and strength to conquer the elements and populate cities.
However, like any other primitive structure produced by evolution, this instinct is by no means perfect. While it has, overall, promoted the advancement of the human species, it occasionally works against Darwinian survival. For example, in some cases this instinct has prompted human societies to expend resources to assist the elderly, mentally disabled, or terminally ill. It has also prevented human societies from breeding those who are strong and intelligent while killing, or at least sterilizing, those who are weak and stupid.
But now human beings have reached a pivotal point in their evolution. For the first time in history, sentient beings understand the forces that have created them. They can now guide their own evolution. They no longer require love to guide them, because their brains have finally evolved to the point where their reason can better accomplish the aim that this primeval instinct sought blindly to achieve. In other words, if both naturalism and evolution are true, then reason and love are ultimately in conflict.
However, this conclusion seems highly unlikely. No string of reasoning could ever lead me to doubt love, because my faith in love is every bit as strong as my faith in reason. I cannot prove that it is wrong to kill a handicapped child, just as I cannot prove the law of non-contradiction. However, though I cannot prove either proposition, I am equally certain that both are true. Therefore, because I am certain that both love and reason are valid, I am certain that naturalism and evolution cannot both be true.