Abstract Natural law theories affirm that it belongs to the nature of law to be apt to promote the common good or do something similar. I defend a weak version of this thesis according to which part of what constitutes something as a nondefective central case of a posited law is that it is apt to promote the common good. Just as the rules of Pictionary require the drawing player to design her drawing to reveal the word in play, the rules of a central case of a legal system require lawmakers to design laws to promote the common good. Therefore, just as a Pictionary drawing that is inapt to reveal the word in play is defective, a central case of a posited law that is inapt to promote the common good is defective.