“It is often said that all the conditions for the first production of a living organism are now present, which could have ever been present. But if (and oh! what a big if!) we could conceive in some warm pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, &c., present, that a proteine compound was chemically formed ready to undergo still more complex changes, at the present day such matter would be instantly devoured or absorbed, which would not have been the case before living creatures were formed.”

“By considering the embryological structure of man - the homologies which he presents with the lower animals - the rudiments which he retains - and the reversions to which he is liable, we can partly recall in imagination the former condition of our early progenitors; and we can approximately place them in their proper position in the zoological series. We thus learnt that man is descended from a hairy quadruped, furnished with a tail and pointed ears, probably arboreal in its habit, and an inhabitant of the Old World. This creature, if its whole structure had been examined by a naturalist, would have been classed among the Quadrumana, as surely as would be the common and still more ancient progenitor of the Old and New World monkeys.”

“The preservation of favourable variations and the rejection of injurious variations, I call Natural Selection, or Survival of the Fittest. Variations neither useful nor injurious would not be affected by natural selection and would be left a fluctuating element.”

“In the struggle for survival, the fittest win out at the expense of their rivals because they succeed in adapting themselves best to their environment.”

“I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection”

“If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive slight modifications, my theory would absolutely break down.”

“False views, if supported by some evidence, do little harm, for everyone takes a salutary pleasure in proving their falseness.”

“Great is the power of steady misrepresentation - but the history of science shows how, fortunately, this power does not endure long.”

“I see no good reasons why the views given in this volume should shock the religious feelings of anyone.”

“My mind seems to have become a kind of machine for grinding general laws out of large collections of facts.”

“Till facts be grouped and called there can be no prediction. The only advantage of discovering laws is to foretell what will happen and to see the bearing of scattered facts.”

“I worked on true Baconian principles, and without any theory collected facts.”

“...I believe there exists, & I feel within me, an instinct for the truth, or knowledge or discovery, of something of the same nature as the instinct of virtue, & that our having such an instinct is reason enough for scientific researches without any practical results ever ensuing from them.”

“The evolution of the human race will not be accomplished in the ten thousand years of tame animals, but in the million years of wild animals, because man is, and always will be, a wild animal.”

“Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science.”

“Man with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men but to the humblest living creature, with his god-like intellect which has penetrated into the movements and constitution of the solar system - with all these exalted powers - Man still bears in his bodily frame the indelible stamp of his lowly origin.”

“On becoming very intimate with Fitz-Roy, I heard that I had run a very narrow risk of being rejected, on account of the shape of my nose! He was an ardent disciple of Lavater, and was convinced that he could judge a man's character by the outline of his features. He doubted whether anyone with my nose could possess sufficient energy and determination for the voyage. I think he was well-satisfied that my nose had spoken falsely.”

“We can allow satellites, planets, suns, universe, nay whole systems of universe[s,] to be governed by laws, but the smallest insect, we wish to be created at once by special act”

“Ignorance more frequently begets confidence than does knowledge: it is those who know little, and not those who know much , who so positively assert that this or that problem will never be solved by science”

“To suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree. Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real”

“doing what little one can to increase the general stock of knowledge is as respectable an object of life, as one can in any likelihood pursue”

“Nothing before had ever made me thoroughly realise, though I had read various scientific books, that science consists in grouping facts so that general laws or conclusions may be drawn from them.”

“But when on shore, & wandering in the sublime forests, surrounded by views more gorgeous than even Claude ever imagined, I enjoy a delight which none but those who have experienced it can understand - If it is to be done, it must be by studying Humboldt”

“Physiological experiment on animals is justifiable for real investigation, but not for mere damnable and detestable curiosity.”

“The expression often used by Mr. Herbert Spencer of the Survival of the Fittest is more accurate, and is sometimes equally convenient”

“In the future I see open fields for more important researches. Psychology will be securely based on the foundation already laid by Mr. Herbert Spencer, that of the necessary acquirement of each mental power and capacity by graduation.”

“I love fools’ experiments. I am always making them.”

“The highest possible stage in moral culture is when we recognize that we ought to control our thoughts.”

“I have tried lately to read Shakespeare, and found it so intolerably dull that it nauseated me.”

“Animals, whom we have made our slaves, we do not like to consider our equal.”

“The young blush much more freely than the old but not during infancy, which is remarkable, as we know that infants at a very early age redden from passion.”

“Blushing is the most peculiar and most human of human expressions. Monkeys redden from passion but it would take an overwhelming amount of evidence to make us believe that any animal can blush.”

“Why does man regret, even though he may endeavour to banish any such regret, that he has followed the one natural impulse, rather than the other; and why does he further feel that he ought to regret his conduct? Man in this respect differs profoundly from the lower animals.”

“...conscience looks backwards and judges past actions, inducing that kind of dissatisfaction, which if weak we call regret, and if severe remorse.”

“I conclude that the musical notes and rhythms were first acquired by the male or female progenitors of mankind for the sake of charming the opposite sex.”

“I have been speculating last night what makes a man a discoverer of undiscovered things; and a most perplexing problem it is. Many men who are very clever - much cleverer than the discoverers - never originate anything.”

“You will be astonished to find how the whole mental disposition of your children changes with advancing years. A young child and the same when nearly grown, sometimes differ almost as much as do a caterpillar and butterfly.”

“Animals manifestly enjoy excitement, and suffer from annul and may exhibit curiosity.”

“May we not suspect that the vague but very real fears of children, which are quite independent of experience, are the inherited effects of real dangers and abject superstitions during ancient savage times?”

“So in regard to mental qualities, their transmission is manifest in our dogs, horses and other domestic animals. Besides special tastes and habits, general intelligence, courage, bad and good tempers. etc., are certainly transmitted.”

“...he who remains passive when over-whelmed with grief loses his best chance of recovering his elasticity of mind.”

“It is not the conscience which raises a blush, for a man may sincerely regret some slight fault committed in solitude, or he may suffer the deepest remorse for an undetected crime, but he will not blush... It is not the sense of guilt, but the thought that others think or know us to be guilty which crimsons the face.”

“...I have always maintained that, excepting fools, men did not differ much in intellect, only in zeal and hard work; and I still think there is an eminently important difference.”

“It is well-known that those who have charge of young infants, that it is difficult to feel sure when certain movements about their mouths are really expressive; that is when they really smile. Hence I carefully watched my own infants. One of them at the age of forty-five days, and being in a happy frame of mind, smiled... I observed the same thing on the following day: but on the third day the child was not quite well and there was no trace of a smile, and this renders it probable that the previous smiles were real.”

“If Mozart, instead of playing the pianoforte at three years old with wonderfully little practice, had played a tune with no practice at all, he might truly have been said to have done so instinctively.”

“If worms have the power of acquiring some notion, however rude, of the shape of n object and over their burrows, as seems the case, they deserve to be called intelligent; for they act in nearly the same manner as would man under similar circumstances.”

“Jealousy was plainly exhibited when I fondled a large doll, and when I weighed his infant sister, he being then 15½ months old. Seeing how strong a feeling of jealousy is in dogs, it would probably be exhibited by infants at any earlier age than just specified if they were tried in a fitting manner”

Describing laughter: “The sound is produced by a deep inspiration followed by short, interrupted, spasmodic contractions of the chest, and especially the diaphragm... the mouth is open more or less widely, with the corners drawn much backwards, as well as a little upwards; and the upper lip is somewhat raised.”

“If the misery of our poor is caused not by the laws of nature, but by our institutions, great is our sin.”

“As the sense of smell is so intimately connected with that of taste, it is not surprising that an excessively bad odour should excite wretching or vomitting in some persons.”

“I cannot persuade myself that a beneficent and omnipotent God would have designedly created parasitic wasps with the express intention of their feeding within the living bodies of Caterpillars”

“I am a strong advocate for free thought on all subjects, yet it appears to me (whether rightly or wrongly) that direct arguments against christianity & theism produce hardly any effect on the public; & freedom of thought is best promoted by the gradual illumination of men's minds, which follow[s] from the advance of science. It has, therefore, been always my object to avoid writing on religion, & I have confined myself to science. I may, however, have been unduly biassed by the pain which it would give some members of my family, if I aided in any way direct attacks on religion”

On seeing the marsupials in Australia for the first time and comparing them to placental mammals: “An unbeliever ... might exclaim 'Surely two distinct Creators must have been at work'”

“a scientific man ought to have no wishes, no affections, — a mere heart of stone.”

“The fact of evolution is the backbone of biology, and biology is thus in the peculiar position of being a science founded on an improved theory, is it then a science or faith?”