The Logical vs. the Ontological Understanding of Conditions

What is it about?

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 acknowledged to be 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 no sense a condition for P; it is a mere consequence of P.

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