The only possible excuse for this book is that it is an answer to a challenge. Even a bad shot is dignified when he accepts a duel. When some time ago I published a series of hasty but sincere papers, under the name of "Heretics," several critics for whose intellect I have a warm respect (I may mention specially Mr. G.S. Street) said that it was all very well for me to tell everybody to affirm his cosmic theory, but that I had carefully avoided supporting my precepts with example. "I will begin to worry about my philosophy," said Mr. Street, "when Mr. Chesterton has given us his." It was perhaps an incautious suggestion to make to a person only too ready to write books upon the feeblest provocation. But after all, though Mr. Street has inspired and created this book, he need not read it. If he does read it, he will find that in its pages I have attempted in a vague and personal way, in a set of mental pictures rather than in a series of deductions, to state the philosophy in which I have come to believe. I will not call it my philosophy; for I did not make it. God and humanity made it; and it made me.