It is an argument against theories of social Darwinism that emphasize competition and survival of the fittest, and against the romantic depictions by writers such as Jean-Jacques Rousseau, who thought that cooperation was motivated by universal love.

Instead, Kropotkin argues that mutual aid has pragmatic advantages for the survival of human and animal communities and, along with the conscience, has been promoted through natural selection.

Kropotkin considers the importance of mutual aid for prosperity and survival in the animal kingdom, in indigenous and early European societies, in the medieval free cities (especially through the guilds), and in the late 19th century village, labor movement, and impoverished people.

He drew from his firsthand observations of Siberia and Northeast Asia, where he saw that animal populations were limited not by food sources, which were abundant, but rather by harsh weather.

Stephen Jay Gould admired Kropotkin's observations, noting that cooperation, if it increases individual survival, is not ruled out by natural selection, and is in fact encouraged.