 The mark of CA is in their displaying complex emergent behavior, starting from simple atoms following simple local rules. Because of this, CA attract a growing number of researchers from the cognitive and natural sciences willing to study pattern formation and complexity in a pure, abstract setting. This entry provides an introduction to CA and focuses on some of their philosophical applications: these range from the philosophy of computation and information processing, to accounts of reduction and emergence in metaphysics and cognition, to debates around the foundations of physics.