-340 – -284
Diodorus Cronus (died c. 284 BCE) was an ancient Greek philosopher of the Megarian-Dialectical school, renowned for his foundational contributions to propositional logic and modal theory. He is best known for the Master Argument (Kyrieuon Logos), which aimed to demonstrate that only what is or will be the case is genuinely possible, collapsing the distinction between possibility and future actuality. His rigorous treatment of conditionals, negation, and temporal modality exercised significant influence on Stoic logic.
Formulated the Master Argument (Kyrieuon Logos) defending logical determinism about future contingents
Defined possibility as 'what is or will be the case,' grounding modal logic in temporal actuality
Developed a strict account of the conditional (sunartesis) requiring necessary connection between antecedent and consequent
Advanced the analysis of motion and time through arguments against infinite divisibility
Influenced Stoic propositional logic, particularly through his student Philo of Megara