"By further reflecting that the clearest evidence would be requisite to make any sane man believe in the miracles by which Christianity is supported,—and that the more we know of the fixed laws of nature the more incredible do miracles become,—that the men at that time were ignorant and credulous to a degree almost incomprehensible by us,—that the Gospels cannot be proven to have been written simultaneously with the events,—that they differ in many important details, far too important, as it seemed to me to be admitted as the usual inaccuracies of eye witnesses;—by such reflections as these, which I give not as having the least novelty or value, but as they influenced me, I gradually came to disbelieve in Christianity as a divine revelation. The fact that many fake religions have spread over large portions of the earth like wildfire had some weight with me. But I was very unwilling to give up my belief; I feel sure of this, for I can remember often and often inventing day-dreams of old letters between distinguished Romans, and manuscripts being discovered at Pompeii or elsewhere, which confirmed in the most striking manner all that was written in the Gospels. But I found it more and more difficult, with free scope given to my imagination, to invent evidence which would suffice to convince me. Thus disbelief crept over me at a very slow rate, but was at last complete. The rate was so slow that I felt no distress, and have never since doubted even for a single second that my conclusion was correct."
( Charles Darwin in his Autobiography of Charles Darwin, Dover Publications, 1992, p. 62. )
"I think that generally (& more & more as I grow older), but not always, that an agnostic would be the most correct description of my state of mind."
( Quoted from Adrian Desmond and James Moore, Darwin: The Life of a Tormented Evolutionist, New York: W. W. Norton & Company, 1991, p. 636. )