The brain in a vat -- Plato's cave -- The veil of perception -- Cogito ergo sum -- Reason and experience -- The tripartite theory of knowledge -- The mind-body problem -- What is it like to be a bat? -- The Turing test -- The ship of Theseus -- Other minds -- Hume's guillotine -- One man's meat ... -- The divine command theory -- The boo/hoorah theory -- Ends and means -- The experience machine -- The categorical imperative -- The golden rule -- Acts and omissions -- Slippery slopes -- Beyond the call of duty -- Is it bad to be unlucky? -- Virtue ethics -- Do animals feel pain? -- Do animals have rights? -- Forms of argument -- The barber paradox -- The gambler's fallacy -- The sorites paradox -- The king of France is bald -- The beetle in the box -- Science and pseudoscience -- Paradigm shifts -- Occam's razor -- What is art? -- The intentional fallacy -- The argument from design -- The cosmological argument -- The ontological argument -- The problem of evil -- The freewill defence -- Faith and reason -- Positive and negative freedom -- The difference principle -- Leviathan -- The prisoner's dilemma -- Theories of punishment -- Lifeboat Earth -- Just war.

An introduction to philosophy focuses on fifty philosophical ideas, from animal rights and the mind-body problem to the freewill defense, the categorical imperative, and the problem of evil.