Before being put into logical form the above statement could have been something like below.

:If Kelly does not finish his homework, he will not go to class
:Kelly did not finish his homework
:Therefore, Kelly will not go to class

The first two statements are the premises while the third is the conclusion derived from them.

Modus tollens

Another form of argument is known as modus tollens (commonly abbreviated MT). In this form, you start with the same