Some examples of valid arguments forms are modus ponens , modus tollens , and disjunctive syllogism . One invalid argument form is affirming the consequent . Just as variables can stand for various numbers in mathematics , variables can stand for various words, or sentences, in logic .
Argument forms are very important in the study of logic.
In a logic course one would learn how to determine what the forms of various sentences and arguments are. The basic notion of argument form can be introduced with an example. Socrates is human. Therefore , Socrates is mortal. B All humans are mortal.