Diodorus Cronus was a Greek philosopher from the 4th century BCE, known for his contributions to logic and metaphysics. He was a member of the Megarian school, which emphasized the importance of dialectical reasoning. Diodorus is particularly noted for his views on the nature of time and the concept of necessity, arguing that the future is fixed and cannot be changed. His most famous argument is the "Master Argument," which challenges the idea of free will by asserting that if something is possible, it must be necessary. Diodorus' ideas influenced later philosophers, including Aristotle and the Stoics, shaping discussions on determinism and free will.