Given “If P, then Q,” denying Q allows us to deny P. Example:
If the sun has risen, it is daytime.
It is not daytime.
Therefore the sun has not risen.
This form is called denying the consequent (modus tollens). It relies on the conditional relation remaining in force.
Opening interactive controls...
Valid form two: deny the consequent
Types of Qiyas: Istithna’i and Iqtirani
Given “If P, then Q,” denying Q allows us to deny P. Example:
If the sun has risen, it is daytime.
It is not daytime.
Therefore the sun has not risen.
This form is called denying the consequent (modus tollens). It relies on the conditional relation remaining in force.