Proving the Validity of Meat Loaf

An exercise we did in class today was to prove Meat Loaf's song, "I Would Do Anything For Love (But I Won't Do That)" using Natural Deduction.

It's not hard to do, provided you understand three rules: Simplification, Conjunction, and Commutativity.

Simplification says that when two propositions are joined together with an "and," "but," or any conjoining operative, you can assert the first proposition by itself.  So, for instance, if you have "Mike is hot and Mike is tall," you can use simplification to just assert "Mike is hot."  Just as this phrase is absolutely true in the complex proposition that has two simple propositions, it is absolutely true by itself.

Conjunction says that if you have two simple distinct ideas: "Mike is hot" and "Mike is tall," you can put them together and say, simply, "Mike is hot and Mike is tall."  They hold as much truth value separately as they do together.

The Commutativity merely means that, in certain cases, you can switch the order of certain propositions without changing their truth value.  One example is "Mike is hot and Mike is tall" can be expressed as "Mike is tall and Mike is hot" without changing its truth value.

So, now we can prove Meat Loaf's wisdom to be valid:

1. And I would do anything for love
2. I’d run right into hell and back
3. I would do anything for love
4. I’ll never lie to you and that’s a fact, but I’ll never stop dreaming of you every night of my life -- Oh no -- no way --

Conclusion:  I would do anything for love, but I won’t do that.

We can symbolize it as follows, with the ~'s meaning 'not':

1.  A
2.  R
3.  A
4.  ~ L dot (and) ~ D     /  And the conclusion: A dot ~ D  ("That" refers to "I'll never stop dreaming...")

So, using our rules...

5.  ~ D dot ~ L  (Commutative, line 4)
6.  ~ D  (Simplification, line 5)
7.  A dot ~ D  (Conjunction, lines 1 and 6)

And there you have it: Meat Loaf ain't lying when he says he'll do anything for love, with the exception of THAT!!!