Modus Ponendo Tollens/Variant/Formulation 1

Theorem
If two statements can not both be true, and one of them is true, it follows that the other one is not true.
 * $\neg \left({p \land q}\right) \dashv \vdash p \implies \neg q$

This theorem is known as the modus ponendo tollens.

Its abbreviation in a tableau proof is $\mathrm {MPT}$.

This can be expressed as two separate theorems: