EliminationThe following argument forms are valid:a. b These argument forms say that when...

Elimination

The following argument forms are valid:

a.

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b

These argument forms say that when you have only two possibilities and you can rule one out, the other must be the case. For instance, suppose you know that for a particular number x, x– 3 =0 or x + 2 = 0.

If you also know that x is not negative, then x = –2, so

x + 2 = 0.

By elimination, you can then conclude that

∴ x – 3 = 0.