This chapter explores Alan Turing’s foundational contributions to computer science and the philosophy of artificial intelligence. Turing introduced the concept of the Turing machine—an abstract computational model using an infinite tape and a read/write head to perform algorithmic operations—and famously proved the halting problem, showing that no general algorithm can determine whether an arbitrary program will halt or run indefinitely. Building on these ideas, Turing introduced the imitation game, now known as the Turing test, as a practical benchmark for machine intelligence: if a machine can hold a conversation well enough that we cannot tell it apart from a human, it has passed. Anticipating critiques from physical, mathematical, theological, and philosophical angles, Turing confronted questions about whether machines can truly replicate human thought or merely simulate it. We examine these debates, focusing on the deeper issues they raise about the nature of intelligence, understanding, and consciousness—and the criteria by which we recognize them in both human and artificial minds.