The fourth and final member of the quartet is Herbert Spencer. Listed as a philosopher, he is best known as the inventor of the new 'science' of Sociology, and tagged 'The Father of Sociology'. As such, he is not very popular with my younger son, who ended up taking GCSE Sociology as a result of his preferred choice clashing with his main option! He was left with either Sociology or German, and as he hadn't done any German up to that point...
Spencer was a contempory of, and rival to, Charles Darwin, devising his own theory of evolution which preceded Darwin's, but lacked some key elements. It was Spencer who popularised the term evolution and who introduced the phrase survival of the fittest.
For Spencer, though, the focus of his theories was on human behaviour and adaptation to circumstances. He studied man's place in society and the functions of the state, writing books with titles like:
The Study of Sociology, 1880.
The Man versus the State, 1884. and
Essays, Scientific, Political and Speculative, 1892.
I must admit that none of these really make me want to rush out and add to my library, but perhaps I am negatively influenced by my own memories of Sociology A level. Not the best choice I have ever made!
Post script: Just had a thought - Herbert Spencer doesn't seem to have had any connection with the Silk Mill. That's novel!