C.S. Lewis's moral argument for the existence of God as described in his book Mere Christianity, can be broken up into three steps. These steps are as follows. There is a universal moral law, then if there is a universal moral law, there must be a universal moral lawgiver, therefore there must be a God.
C.S. Lewis establishes that there is a moral law or else all moral disagreements would make no sense. Lewis points out that we appeal to universal moral standard all the time so we do not have to explain why things are morally bad or evil. He gives an example of a psychiotic murdered torturing, raping, and killing him victims and how we respond by saying "that's evil". If there were not any moral standards then moral judgements would not be meaningful and barbaric actions such as Hitler killing Jews would just be a difference of opinion.
He goes on to say that moral laws are not entailed by any physical, natural features of the universe so the best way to answer to explaining moral law is that there must be a universal law giver. He says "the kind of being to which moral law points to would be supremely powerful, perfectly good, and a being who is interested in our behavior." In other words, the law giver is God.
If you believe his first two premises, then it logically follows that God is the law giver unless one of his premises is false. He gives examples of how people might think that one of his premises is false. He says his second premise could be false by saying moral law can be explained by "herd instinct," such as survival of the fittest. We would tend to act on our strongest moral impulse but that is not always the right thing to do. He explains how morality cannot come from a social convention because the society sets its moral standards so we can not know if the society has improved. If it does, then Martin Luther King Jr. would be a morally evil person since he opposed what is established according to societies conventions. Then, he says morality cannot be self imposed because the person giving himself the morals would act like the law giver and have morality on his own terms. He concludes by saying that there cannot not be a moral law because it is impressed upon us.
C.S. Lewis did not use any historical examples but he did give us some recent examples such as Martin Luther King Jr. and Adolf Hitler.
I agree with what C.S. Lewis says because he thinks about how people could disagree with his premises and then he shows us that these are false ideas and that his premises are actually true. Because of this, I find his argument to be very logical in understanding if God exists.
Sources:
The Moral Argument for God's Existence
Moral Arguments for the Existence of God
