I am not disposed to bewail the limitations imposed by human ignorance. On the contrary, I feel ignorance is a healthful stimulant; and my enforced conviction that neither I nor anyone can possibly lay down beforehand what does not exist in the universe, or even what is not going on all round us everyday of our lives, leaves me with a cheerful hope that something very new and very arresting may turn up anywhere at any minute. … I shall try to utilize this temper of mind today by clearing away, so far as I can, certain presuppositions, on one side or on the other, which seem to me to depend upon a too hasty assumption that we know more about the universe than as yet we really can know.

Address to the Society for Psychical Research (1897)