his 1651 book Leviathan established social contract theory, the foundation of most later Western political philosophy
developed fundamentals of European liberal thought
he purposed to unite the separate phenomena of Body, Man, & State
he went on to conceive the system of thought to the elaboration of which he would devote his life
built a good reputation in philosophic circles & in 1645 was chosen with Descartes, Gilles de Roberval & others, to referee the controversy between John Pell & Longomontanus over the problem of squaring the circle
believed people are naturally selfish, cruel, and greedy
said the government was needed to protect people from their own selfishness