All you need to know about the central ideas of philosophy. In a series of accessible and engaging essays, 50 Philosophy Ideas You Really Need to Know introduces and explains the problems of knowledge, consciousness, identity, ethics, belief, justice and aesthetics that have troubled the minds of great thinkers for centuries, from the ancient Greeks to the present day. From The brain in a vat to Plato's cave, Cogito ergo sum to The mind-body problem, this compact guide is the perfect introduction to central ideas of philosophy.