“All men are, at times, influenced by inexplicable sentiments. Ideas haunt them in spite of all their efforts to discard them. Prepossessions are entertained, for which their reason is unable to discover any adequate cause. The strength of a belief, when it is destitute of any rational foundation, seems, of itself, to furnish a new ground for credulity. We first admit a powerful persuasion, and then, from reflecting on the insufficiency of the ground on which it is built, instead of being prompted to dismiss it, we become more forcibly attached to it.”

“No one knows the powers that are latent in his constitution. Called forth by imminent dangers, our efforts frequently exceed our most sanguine belief.”

“There is no standard by which time can be measured, but the succession of our thoughts, and the changes that take place in the external world.”

“How slender is the accommodation which nature has provided for man.”

“‎"The incapacity of sound sleep denotes a mind sorely wounded.”

“Bless the bright eyes of your sex! They never see, whether for good or bad, more than one side of any question; and that is always, the one which first presents itself to them.”

“...Whilst on board the Beagle I was quite orthodox, and I remember being heartily laughed at by several of the officers... for quoting the Bible as an unanswerable authority on some point of morality... But I had gradually come by this time, i.e., 1836 to 1839, to see that the Old Testament from its manifestly false history of the world, with the Tower of Babel, the rainbow at sign, &c., &c., 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, (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 uncomprehensible by us, that the Gospels cannot be proved 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 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. The fact that many false religions have spread over large portions of the earth like wild-fire had some weight with me. Beautiful as is the morality of the New Testament, it can be hardly denied that its perfection depends in part on the interpretation which we now put on metaphors and allegories.But I was very unwilling to give up my belief... 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. 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 everlastingly punished. And this is a damnable doctrine.”