From Karen Armstrong’s A History of God: The 4,000-Year Quest of Judaism, Christianity and Islam:

Today many people in the West would be dismayed if a leading theologian suggested that God was in some profound sense a product of the imagination.  Yet it should be obvious that the imagination is the chief religious faculty.  It has been defined by Jean-Paul Sartre as the ability to think of what is not. … The idea of God, however it is defined is perhaps the prime example of an absent reality which, despite its inbuilt problems, has continued to inspire men and women for thousands of years.  The only we we can conceive of God, who remains imperceptible to the senses and to logical proof, is by means of symbol, which it is the chief function of the imaginative mind to interpret.