"Whilst on board the Beagle I was quite orthodox, and I remember being heartily laughed at by several of the officers (though themselves orthodox) for quoting the Bible as an unanswerable authority on some point of morality. I suppose it was the noveltry of the argument that amused them. But I had gradually come, by this time, to see that the Old Testament from its manifestly false history of the world, with the Tower of Babel, the rainbow at sign, etc., etc., and from its attributing to God the feelings of a revengeful tyrant, was no more to be trusted than the sacred books of the Hindoos, or the beliefs of any barbarian."
"By further reflecting that the clearest evidence would be requisite to make any sane man believe in the miracles by which Christianity is supported, -- 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 proved to have been written simultaneous 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 eyewitnesses; -- 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."
"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 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. I can indeed hardly see how anyone ought to wish Christianity to be true; for if so the plain language of the text seems to show that the men who do not believe, and this would include my Father, Brother and almost all of my friends, will be everlasting punished. And this is a damnable doctrine." - Charles Darwin