Survival of the Fittest?

 Social Darwinism is a social theory that connects Darwin's theory of evolution by natural selection and the social relations of humanity. Raskolnikov survives because he confesses. He is saved because he chooses to be, and this makes him fit to be alive. Svidrigailov, Alyona and Lizaveta all die because they are not fit to withstand the hardships of society. When Raskolnikov talks about the men with great amounts of power, he feels that they have that power for a reason; they are born with it, and no amount of struggle can change it.