The core of The Vital Science is four interlocking chapters which examine certain ideas emerging from the new biology which particularly appealed to literary minds: evolutionism - the philosophy that organic adaptation is progressive in a human sense; degeneration - the belief that parasitism and retrogression are as applicable in the human sphere as in accounts of the extinction of species; eugenics - progress can be assured by aping nature's methods; and theories of heredity - read variously as encouraging or denying attempts to escape one's genetic destiny. Such ideas were used by many novelists, belles lettristes and journalists to warn, abuse, encourage or inspire, and the discussion ranges widely from minor utopian fiction to major novels by H.G. Wells, Samuel Butler and Thomas Hardy. The Vital Science is designed to interest historians and readers who will enjoy approaching the Victorian era from an unfamiliar angle as well as historians of biological theory between The Origin of Species and Mendel.

Parts of the book have been anthologised in textbooks and along with Gillian Beer's Darwin's plots it has become a standard text in its field.