The talk will explain why category theory is of interest for developers, taking examples from Java and Haskell, and referencing the new blockchain scripting languages Simplicity, Michelson, and Plutus. The principle of Propositions as Types describes a correspondence between, on the one hand, propositions and proofs in logic, and, on the other, types and programs in computing. And, on the third hand, we have category theory! Assuming only high school maths, the talk will explain how categories model three basic data types: products (logical and), sums (logical or), and functions (logical implication). And it explains why you already learned the most important stuff in high school. Speaker: Philip Wadler