‘Why causation?’ introduces the reader to one of the core topics in philosophy, but which is important to everyone whether a scientist, social scientist, or philosopher. The key theories of causation and the surrounding debates and controversies are discussed. What is it for one thing to cause another? Do causes produce their effects by guaranteeing them? Do causes have to precede their effects? Can causation be reduced to the forces of physics? And are we right to think of causation as one single thing at all?