Pythagoras coined the term "philosophy" to mean "love of wisdom". Philosophy involves critically examining fundamental questions about existence, knowledge, values, reason, and language. It can be understood as a set of beliefs about life, a process of reflection and criticism of beliefs, or an attempt to understand the world as a whole. The main branches of philosophy are logic, metaphysics, epistemology, and value theory, which includes ethics, aesthetics, and social/political philosophy.