Argument from morality

Portrait of Immanuel Kant, who proposed an argument for the existence of God from morality

In his Critique of Pure Reason, German philosopher Immanuel Kant stated that no successful argument for God's existence arises from reason alone. In his Critique of Practical Reason he went on to argue that, despite the failure of these arguments, morality requires that God's existence is assumed, owing to practical reason.[6] Rather than proving the existence of God, Kant was attempting to demonstrate that all moral thought requires the assumption that God exists.[7] Kant argued that humans are obliged to bring about the summum bonum: the two central aims of moral virtue and happiness, where happiness arises out of virtue. As ought implies can, Kant argued, it must be possible for the summum bonum to be achieved.[5] He accepted that it is not within the power of humans to bring the summum bonum about, because we cannot ensure that virtue always leads to happiness, so there must be a higher power who has the power to create an afterlife where virtue can be rewarded by happiness.[6]

Philosopher G. H. R. Parkinson notes a common objection to Kant's argument: that what ought to be done does not necessarily entail that it is possible. He also argues that alternative conceptions of morality exist which do not rely on the assumptions that Kant makes – he cites utilitarianism as an example which does not require the summum bonum.[8] Nicholas Everitt argues that much moral guidance is unattainable, such as the Biblical command to be Christ-like. He proposes that Kant's first two premises only entail that we must try to achieve the perfect good, not that it is actually attainable.[9]

Both theists and non-theists have accepted that the existence of objective moral truths might entail the existence of God. Atheist philosopher J. L. Mackie accepted that, if objective moral truths existed, they would warrant a supernatural explanation. Scottish philosopher W. R. Sorley presented the following argument:

1. If morality is objective and absolute, God must exist.
2. Morality is objective and absolute.
3. Therefore, God must exist.[10]

Many critics have challenged the second premise of this argument, by offering a biological and sociological account of the development of human morality which suggests that it is neither objective nor absolute. This account, supported by biologist E. O. Wilson and philosopher Michael Ruse, proposes that the human experience of morality is a by-product of natural selection, a theory philosopher Mark D. Linville calls evolutionary naturalism. According to the theory, the human experience of moral obligations was the result of evolutionary pressures, which attached a sense of morality to human psychology because it was useful for moral development; this entails that moral values do not exist independently of the human mind. Morality might be better understood as an evolutionary imperative in order to propagate genes and ultimately reproduce. No human society today advocates immorality, such as theft or murder, because it would undoubtedly lead to the end of that particular society and any chance for future survival of offspring. Scottish empiricist David Hume made a similar argument, that belief in objective moral truths is unwarranted and to discuss them is meaningless.[11]

Because evolutionary naturalism proposes an empirical account of morality, it does not require morality to exist objectively; Linville considers the view that this will lead to moral scepticism or antirealism.[12][13] C. S. Lewis argued that, if evolutionary naturalism is accepted, human morality cannot be described as absolute and objective because moral statements cannot be right or wrong. Despite this, Lewis argued, those who accept evolutionary naturalism still act as if objective moral truths exist, leading Lewis to reject naturalism as incoherent.[14] As an alternative ethical theory, Lewis offered a form of divine command theory which equated God with goodness and treated goodness as an essential part of reality, thus asserting God's existence.[15]

J.C.A. Gaskin challenges the first premise of the argument from moral objectivity, arguing that it must be shown why absolute and objective morality entails that morality is commanded by God, rather than simply a human invention. It could be the consent of humanity that gives it moral force, for example.[8] American philosopher Michael Martin argues that it is not necessarily true that objective moral truths must entail the existence of God, suggesting that there could be alternative explanations: he argues that naturalism may be an acceptable explanation and, even if a supernatural explanation is necessary, it does not have to be God (polytheism is a viable alternative). Martin also argues that a non-objective account of ethics might be acceptable and challenges the view that a subjective account of morality would lead to moral anarchy.[10]

William Lane Craig has argued for this form of the moral argument.[16]

Portrait of John Henry Newman, who used the conscience as evidence of the existence of God

Related to the argument from morality is the argument from conscience, associated with eighteenth-century bishop Joseph Butler and nineteenth-century cardinal John Henry Newman.[8] Newman proposed that the conscience, as well as giving moral guidance, provides evidence of objective moral truths which must be supported by the divine. He argued that emotivism is an inadequate explanation of the human experience of morality because people avoid acting immorally, even when it might be in their interests. Newman proposed that, to explain the conscience, God must exist.[17]

British philosopher John Locke argued that moral rules cannot be established from conscience because the differences in people's consciences would lead to contradictions. Locke also noted that the conscience is influenced by "education, company, and customs of the country", a criticism mounted by J. L. Mackie, who argued that the conscience should be seen as an "introjection" of other people into an agent's mind.[18] Michael Martin challenges the argument from conscience with a naturalistic account of conscience, arguing that naturalism provides an adequate explanation for the conscience without the need for God's existence. He uses the example of the internalization by humans of social pressures, which leads to the fear of going against these norms. Even if a supernatural cause is required, he argues, it could be something other than God; this would mean that the phenomenon of the conscience is no more supportive of monotheism than polytheism.[17]

C. S. Lewis argues for the existence of God in a similar way in his book Mere Christianity, but he does not directly refer to it as the argument from morality.