This document discusses natural deduction and the rules of Boolean logic and formal proofs. It introduces natural deduction as a proof calculus that uses inference rules to model human reasoning. The document then explains introduction and elimination rules for conjunction, disjunction, negation and the contradiction symbol ⊥. It notes that the rules allow deducing ⊥ from a tautological, logical or meaning-based contradiction. The document emphasizes being careful with the rules, finding counterexamples if deductions don't make sense, and formalizing proofs by tracking arguments back to their sources. It also notes that at times deductions can be made without premises.