If the people of Europe had known as much of astronomy and geology when the bible was introduced among them, as they do now, there never could have been one believer in the doctrine of inspiration. If the writers of the various parts of the bible had known as much about the sciences as is now known by every intelligent man, the book never could have been written. It was produced by ignorance, and has been believed and defended by its author. It has lost power in the proportion that man has gained knowledge. A few years ago, this book was appealed to in the settlement of all scientific questions; but now, even the clergy confess that in such matters, it has ceased to speak with the voice of authority. For the establishment of facts, the word of man is now considered far better than the word of God. In the world of science, Jehovah was superseded by Copernicus, Galileo, and Kepler. All that God told Moses, admitting the entire account to be true, is dust and ashes compared to the discoveries of Descartes, Laplace, and Humboldt. In matters of fact, the bible has ceased to be regarded as a standard. Science has succeeded in breaking the chains of theology. A few years ago, Science endeavored to show that it was not inconsistent with the bible. The tables have been turned, and now, Religion is endeavoring to prove that the bible is not inconsistent with Science. The standard has been changed.

The most detestable wickedness, the most horrid cruelties, and the greatest miseries, that have afflicted the human race have had their origin in this thing called revelation, or revealed religion. It has been the most dishonourable belief against the character of the divinity, the most destructive to morality, and the peace and happiness of man, that ever was propagated since man began to exist. It is better, far better, that we admitted, if it were possible, a thousand devils to roam at large, and to preach publicly the doctrine of devils, if there were any such, than that we permitted one such impostor and monster as Moses, Joshua, Samuel, and the Bible prophets, to come with the pretended word of God in his mouth, and have credit among us.Whence arose all the horrid assassinations of whole nations of men, women, and infants, with which the Bible is filled; and the bloody persecutions, and tortures unto death and religious wars, that since that time have laid Europe in blood and ashes; whence arose they, but from this impious thing called revealed religion, and this monstrous belief that God has spoken to man? The lies of the Bible have been the cause of the one, and the lies of the Testament of the other.

...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.