Is religion is necessary because otherwise people would be free to do evil?

A good example of people acquiring religion in a jail has been portrayed in "The Clockwork Orange."

The 20th century's foremost popularizer of Christianity, C. S. Lewis, held that morality is _logical_ and thus can be known without religion. See his short (three chapters) book _The Abolition of Man_.

(He also says that when he began his studies at Oxford after getting out of the British army after the first world war, his notions of morality were limited to despising stinginess with money and a few similar things. I've wondered why he volunteered for the army and for combat if not out of moral considerations. He saw a fair amount of combat and was nearly killed in action and subsequently hospitalized for several months. As an Irishman he was not subject to conscription despite the fact that Ireland was then part of the United Kingdom. It seems strange that he says he had little sense of morality at that time, and he volunteered even though he hated participating in the war.)