Solidarity of causes in the world, 216. The human mind abstracts
in order to explain, 219. Different cycles of operation in
Nature, 220. Darwin's distinction between causes that produce
and causes that preserve a variation, 221. Physiological causes
produce, the environment only adopts or preserves, great men,
225. When adopted they become social ferments, 226. Messrs.
{xvii}
Spencer and Allen criticised, 232. Messrs. Wallace and
Gryzanowski quoted, 239. The laws of history, 244. Mental
evolution, 245. Analogy between original ideas and Darwin's
accidental variations, 247. Criticism of Spencer's views, 251.