Though argument does not create conviction, the lack of it destroys belief. What seems to be proved may not be embraced; but what no one shows the ability to defend is quickly abandoned. Rational argument does not create belief, but it maintains a climate in which belief may flourish.
Austin Farrer, “The Christian Apologist,” in Light on C.S. Lewis, ed., Jocelyn Gibb (Harcourt, Brace & World, 1965), pgs 26