Biography must not degenerate into hagiography and the faults must not be concealed. But they must not be writ large. The reader should be enabled to enter into the subject’s mind and world, to see situations from his point of view, and yet to retain his own moral judgment and condemn what is wrong for himself and without the author’s perpetual strictures. When once I told a continental scholar that I was writing a life of Dr Flew, he licked his lips at the thought of all the files, crammed with ecumenical memoranda and lecture notes, which were waiting for me to devour. But Dr Flew did not belong to the age of large secretarial staffs and mechanical aids, nor did he have a card-index mentality. He left few documents (or literary remains), but there are many letters to his mother and some to his friends. He was a brilliant letter-writer as well as a very faithful one, and these, nearly all in his own hand and many somewhat yellow with the years, have been a chief quarry. Otherwise it has been a matter of sleuth-like deduction, a piecing together of facts from people’s reminiscences, contemporary books and records, and one’s own memories. –From the Preface