Negation introduction

Negation Introduction, often abbreviated as "¬I" or "NI," is a rule in formal logic, specifically in natural deduction systems. It is used to derive a negation (not) of a proposition based on a contradiction that arises from the assumption of that proposition. The rule can be summarized as follows: 1. **Assume the Proposition (P)**: You assume that a certain proposition \( P \) is true.