This is about the 3rd line of the truth table of the implication: | A | B | A -> B | | T | T | T | | T | F | F | | F | T | T | | F | F

This is about the 3rd line of the truth table of the implication: | A | B | A -> B | | T | T | T | | T | F | F | | F | T | T | | F | F | T | If A is false and B is true, then A => B is true. Which essentially means: you can get to the truth from a false premise. For instance, supposing that 1=2, it is possible to multiply both sides by zero to prove that 0=0.