Rules of inference and symbolic logic.
Take, for example, the following argument with 1 as the original premise, and 2 through 5 as rules of inference:
- A or ~B · addition
- ~B or A · commutative
- ~(~B) → A · material implication
- Therefore, B → A · double negation
Now replace A and B with the following statements: A = apples taste delicious, and B = Batman exists. Let’s translate the above argument:
- Apples taste delicious
- Either apples taste delicious, or it’s not the case that Batman exists
- Either it’s not the case that Batman exists, or apples taste delicious
- If it’s not not the case that Batman exists, then apples taste delicious
- Therefore, if Batman exists, then apples taste delicious
It makes no sense. But it follows the rules of logic.