Aristotle called it "arche" - the starting point, the first principle from which all other knowledge flows. Identifying these fundamental truths is the core skill of first principles thinking.

A fundamental truth is something that cannot be deduced from anything more basic - it stands on its own. It is distinct from an opinion (which may be wrong), a belief (which rests on assumptions), or an analogy (which borrows from other contexts). Finding these irreducible components requires disciplined decomposition and careful verification.

In this topic, you will learn to break down problems into their constituent parts, distinguish facts from beliefs, and identify the bedrock truths that form the foundation for rigorous reasoning.