Developed by Charles Darwin, social Darwinism is a theory of biological evolution, arguing that all species of organisms arise and develop through natural selection, emphasising competition and survival of the fittest. Darwinism is usually used to support reactionary political and ideological positions, and has even influenced revolutionary political ideologies such as Marxism. Peter Kropotkin, through his book Mutual Aid, critiques Darwin’s evolutionary theory, arguing that social interactions in nature are not limited to a constant struggle for life or pure antagonism, instead, social cooperation determines mutual survival.