It builds upon the principal theory of George C. Williams's first book Adaptation and Natural Selection. Dawkins coined the term selfish gene as a way of expressing the gene-centered view of evolution, which holds that evolution is best viewed as acting on genes, and that selection at the level of organisms or populations almost never overrides selection based on genes. An organism is expected to evolve to maximize its inclusive fitness – the number of copies of its genes passed on globally (rather than by a particular individual). As a result, populations will tend towards an evolutionarily stable strategy.
The fundamental purpose of Dawkins' book is to account for one of the most serious contradictions to Darwinism, the existence of altruism in nature (see Counterexamples to Evolution). To do so, he simply denies that altruism truly exists, and attempts to account for its perceived occurrence by reducing all animal behavior to selfishness, with increasingly twisted logic. As critics noted, his work is extremely speculative and shy on evidence, but was glorified by atheists as it agreed with their worldview. As such, The Selfish Gene has become lauded by the atheist Darwinist movement, but otherwise largely ignored by the general public.
The book also coins the term meme for a unit of human cultural evolution analogous to the gene, suggesting that such "selfish" replication may also model human culture, in a different sense. Memes were Dawkins' attempt to provide a scientific-sounding basis for cultural relativism and atheistic denial of religion, by reducing all matters of faith to a matter of "memes." "Memetics" has since become a favorite area of study for militant atheists such as Daniel Dennett.