Relations and Identity

Our third rule for forming quantificational wffs introduces “=a” (“equals”):

3. The result of writing a small letter and then “=a” and then a small letter is a wff.

This rule lets us construct wffs like these:

x=y r=l Àp=l

= = =

x equals y. Romeo is the lover of Juliet. Paris isn’t the lover of Juliet.