Introduction to Logic

Exercise 2.2 - Friends

Consider a variation of the Sorority World example in which we have a single binary relation, called friend. friend differs from likes in two ways. It is irreflexive, i.e. a person cannot be friends with herself; and it is symmetric, i.e. if one person is a friend of a second person, then the second person is friends with the first. The table on the left below illustrates one state of the friend relation (which does not satisfy these properties), and the dataset on the right shows the corresponding information as sentential data. You can click on the squares in the table to check or uncheck those squares, and the dataset on the right changes accordingly. Your mission is to change the table on the left so that it satisfies the irreflexivity and symmetry of the friend relation and exactly six friend facts are true. Note that there are multiple ways in which this can be done.

  Abby Bess Cody Dana
Abby
Bess      
Cody      
Dana