## The Propositional Calculus

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• 18.6k
And the most complete text I've come across:

THE OPEN LOGIC TEXT

Wish I'd seen this earlier.
• 7.6k
Prove P via Reductio Ad Absurdum.

1. ~P $\to \bot$

2. ~~P $\lor \bot$ [1 ME]

3. P $\lor \bot$ [2 DN]

4. $\bot$ is false

Ergo,

5. P hasta be true [since P $\lor \bot$ (line 3) is true]

QED

:chin:
• 1.7k

Pretty much, you proved P from the premise ~~P. Congratulations. And your point is?
• 7.6k
Just trying to make sense of RAA.

There's another way of showing why RAA works.
• 1.7k
Just trying to make sense of RAA.

Just look at the truth table.

Anyway, you didn't use RAA.
• 7.6k
Just look at the truth table.

Anyway, you didn't use RAA.

:chin:
• 1.7k
I don't know what that emoji means. I take it though that it doesn't indicate anything substantive.
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