Some people believe that humanity invented God out of need - to cope with the uncertainties of a confusing and often dangerous world. The psychological explanation for God is one of the most common arguments against Christian faith (and against any theistic religion). Belief in a god is common to all cultures in all time periods. Atheists prefer to explain this as "wish fulfilment" - that humanity invented God because we wished God existed.
Lewis responded to the influential atheists of his time - Ludwig Feuerbach (1804 - 1872), Karl Marx (1818 - 1883) and Sigmund Freud (1856 - 1939). Lewis showed that wishing for something does not make it true or real. On the other hand, the wish itself does not prove that what we desire does not exist. If we are hungry, we wish for food. Fortunately, food exists to satisfy your wish. The same thing could be said about thirst and sleep.
Lewis experienced sharp longings for something beyond his ordinary life and came to conclude that "If I find in myself a desire which no experience in this world can satisfy, the most probable explanation is that I was made for another world." Our pleasures on earth act as cosmic pointers to those realities that will ultimately satisfy us.
Yes, religion can be a projection of some human experience onto God. We can wish God to be as we wish him to be. However, an argument against abuse is not argument against appropriate use. Just because we wish for something doesn't make it untrue.
Lewis also indicated that the tables can be turned on the atheist. Is atheism a project, a desire to kill God, to be free from accountability to a higher power, an opiate for the conscience to escape moral guilt, a wish fulfilment? When we repress something, at a deeper level we know it is really true. Lewis believed that denial of God was a result of systematic dishonesty and was fundamentally self-refuting.
[Summarised from Chapter 9 of Art Lindsley's C.S. Lewis' Case for Christ]
Lewis coined a term called "bulverism" to describe a logical fallacy in which, rather than proving that an argument is wrong, a person instead assumes it is wrong, and then goes on to explain why the other person held that argument. Lewis wrote about this in a 1941 essay of the same name, later included in the anthology God in the Dock. He explains the origin of this term:
You must show that a man is wrong before you start explaining why he is wrong. The modern method is to assume without discussion that he is wrong and then distract his attention from this (the only real issue) by busily explaining how he became so silly. In the course of the last fifteen years I have found this vice so common that I have had to invent a name for it. I call it "Bulverism". Some day I am going to write the biography of its imaginary inventor, Ezekiel Bulver, whose destiny was determined at the age of five when he heard his mother say to his father — who had been maintaining that two sides of a triangle were together greater than a third — "Oh you say that because you are a man." "At that moment", E. Bulver assures us, "there flashed across my opening mind the great truth that refutation is no necessary part of argument. Assume that your opponent is wrong, and the world will be at your feet. Attempt to prove that he is wrong or (worse still) try to find out whether he is wrong or right, and the national dynamism of our age will thrust you to the wall." That is how Bulver became one of the makers of the Twentieth Century.
Lewis gives this example in his article on "Bulverism" ...
Suppose I think, after doing my accounts, that I have a large balance at the bank. And suppose you want to find out whether this belief of mine is "wishful thinking." You can never come to any conclusion by examining my psychological condition. Your only chance of finding out is to sit down and work through the sum yourself. When you have checked my figures, then, and then only, will you know whether I have that balance or not. If you find my arithmetic correct, then no amount of vapouring about my psychological condition can be anything but a waste of time. If you find my arithmetic wrong, then it may be relevant to explain psychologically how I came to be so bad at my arithmetic, and the doctrine of the concealed wish will become relevant — but only after you have yourself done the sum and discovered me to be wrong on purely arithmetical grounds. It is the same with all thinking and all systems of thought. If you try to find out which are tainted by speculating about the wishes of the thinkers, you are merely making a fool of yourself. You must first find out on purely logical grounds which of them do, in fact, break down as arguments. Afterwards, if you like, go on and discover the psychological causes of the error.
Tomorrow ... some thoughts on C.S. Lewis and Post-Modernism