“Restraint, soberness, the matured thought, the unselfish act, they are necessities of the barbarous state, the life of dangers. Dourness is man's tribute to unconquered nature.”

“It is a law of nature we overlook, that intellectual versatility is the compensation for change, danger, and trouble. An animal perfectly in harmony with its environment is a perfect mechanism. Nature never appeals to intelligence until habit and instinct are useless. There is no intelligence where there is no change and no need of change. Only those animals partake of intelligence that have a huge variety of needs and dangers.”

“We are kept keen on the grindstone of pain and necessity.”

“What, unless biological science is a mass of errors, is the cause of human intelligence and vigour? Hardship and freedom: conditions under which the active, strong, and subtle survive and the weaker go to the wall; conditions that put a premium upon the loyal alliance of capable men, upon self-restraint, patience, and decision. And the institution of the family, and the emotions that arise therein, the fierce jealousy, the tenderness for offspring, parental self-devotion, all found their justification and support in the imminent dangers of the young.”

“Man is the unnatural animal, the rebel child of nature, and more and more does he turn himself against the harsh and fitful hand that reared him.”

“With wine and food, the confidence of my own table, and the necessity of reassuring my wife, I grew by insensible degrees courageous and secure.”

“Adapt or perish, now as ever, is nature's inexorable imperative.”