The Principles of Biology by Herbert Spencer (1864) looked at biology in terms of themes, such as Function, Adaptation and Variation. In this book Spencer introduced the expression ‘survival of the fittest’, in the sense of ‘the most appropriate to its environment’. 

What did Spencer’s thinking embrace? 

Spencer was a polymath whose work includes writings on religion, economics, literature, biology, sociology, and political theory. He built an understanding of evolution as the progressive development of all creation from simple forms based on homogeneity towards an integrated equilibrium of differentiated forms, against the theories of Darwin. It also worked against the idea that everything moves towards homogeneity rather than heterogeneity (the second law of thermodynamics). 

Spencer, against the thinking of Darwin, incorporated into his thinking Lamarckian models – the idea that acquired characteristics could be inherited. These models explained the extraordinarily accelerated development of the human species. 

What is understood by ‘social Darwinism’? 

Spencer has been credited with the idea that Darwinian evolution provides a natural justification for the notion that ‘might is right’. In fact he believed that the model for economic competition could be found in competition for resources in nature; but competition could be managed for the good of society, so long as it did not lead to increased power for the state. If private charity led to the support for an idle underclass then it was a failure, an idea that when combined with population management, tends towards support for eugenics.