6 ideas
Individual acts like murder, suicide, and marriage look like products of free choice, yet their annual totals across a society stay remarkably constant year after year. Buckle concludes that such acts are determined by the state of society, and that individual volition cancels out in the aggregate. Looking at a population's numbers rather than at single cases reveals the laws governing human conduct.
Climate, food, soil, and the general aspect of nature are the physical forces that act on a people. The first three determine how wealth is produced and distributed. The last shapes the imagination: overwhelming, dangerous landscapes breed superstition and fear, while milder, more ordered ones encourage reasoning and inquiry.
In hot climates where a nutritious staple such as rice is easy to grow, the labor supply multiplies rapidly and wages fall toward subsistence. Wealth then concentrates in a small elite, and the majority is locked into poverty and political subjection. Buckle cites India, Egypt, and Mexico as cases where natural fertility itself produced extreme inequality.
Moral principles such as doing good and loving your neighbor have hardly changed in thousands of years, so they cannot explain why civilizations advance. Knowledge, by contrast, accumulates and is transmitted, and it changes how people act. Progress therefore follows from the growth and spread of intellectual truths, not from moral exhortation.
Buckle treats paternalistic intervention by governments and churches, through regulating trade, belief, and conduct, as a main barrier to progress. Well-meant protection suppresses the skepticism and free inquiry that let knowledge grow. The best legislation, in his account, has mostly repealed earlier interfering laws rather than creating new ones.
Outside Europe, nature's scale, including earthquakes, vast mountains, tropical storms, and epidemics, overpowered the human mind and subordinated people to their environment. In Europe, a gentler nature let the mind subordinate its surroundings, so mental rather than physical laws increasingly governed development. Buckle uses this contrast to argue that European history must be studied through its intellectual history, with England as the clearest case.