For ten points, identify this British social scientist who coined the phrase "survival of the fittest."
He was the only one of his parents' 9 children who lived to adulthood, and he had an affair with George Eliot.  In 1851, he published Social Statistics which argued for the inevitability of human progress, and in 1855 he wrote Principles of Psychology .  Five years later, he tried to integrate all existing fields of knowledge in his A System of Synthetic Philosophy, arguing that society had evolved from a simple to a more complex state.  For ten points, identify this British social scientist who coined the phrase "survival of the fittest."
He was the only one of his parents' 9 children who lived to adulthood, and he had an affair with George Eliot.  
Herbert Spencer