Followup to Fundamentals of Formalisation Level 4: Formal Semantics Basics. First post.

This is a new lesson of our online course on math formalizations required for AI safety research.

The big ideas:

- Natural Deduction Proof System

To move to the next level you need to be able to:

- Explain the difference between a formal system of proof and our informal notion of proof.
- Derive proofs of logical formula in the system of natural deduction.

Why this is important:

Learning mathematical proof is hard, as you may have experienced in levels 2 and 3. By learning a formal system of proof you will make your own thoughts more rigorous, understand the smallest details that need to be covered to perform a proof, and build your intuition for informal proof.

For every lesson you have 2 options: do the whole thing, or skip to the questions and exercises in the end. The latter option is for people who suspect they already know the subject. It serves as a means of verifying or falsifying that hypothesis.