Tag Archive | Russell

Proving a Negative

In this post, I’m going to attempt to prove a negative:

1) P → Q

2) ¬Q

3) ∴ ¬P

Wow…that was easy. I wonder if I can take it one step further, and prove a universal negative? Hang on to your hats, cause this one is tricky:

1) ∀xPx → ∀xQx

2) ¬∀xQx

3) ∴ ¬∀xPx

Quod Erat Demonstratum.