Use an Euler diagram to determine whether the argument is valid or invalid.

Question

All businessmen wear suits.

Aaron wears a suit.  

                                   

∴Aaron is a businessman

 

A. Valid B. Invalid

Answer 1

Two circles, circle A represents all businessmen; circle B represents all men wearing suits.

Exterior to A are all non-businessmen; exterior to B are all men not wearing suits.

Where A and B intersect we have all businessmen wearing suits, but B also intersects the area external to A, and therefore includes men wearing suits who are not business men. B contains all of A, but A does not contain all of B. That is, A is a subset of B. Aaron belongs to B so he may not be a businessman. The statement is invalid (answer B).