The logical vs. the ontological understanding of conditions.

Abstract

According to the truth-functional analysis of conditions, to be ‘necessary for ’ and ‘sufficient for ’ are converse relations. From this, it follows that to be ‘necessary and sufficient for ’ is a symmetric relation, that is, that if P is a necessary and sufficient condition for Q, then Q is a necessary and sufficient condition for P. This view is contrary to common sense. In this paper, I point out that it is also contrary to a widely accepted ontological view of conditions, according to which if P is a necessary and sufficient condition for Q, then Q is in no sense a condition for P; it is a mere consequence of P.