CONDITION, NECESSARY/SUFFICIENT

If p is a necessary condition of q, then q cannot be true unless p is true. If p is a sufficient condition of q, then given that p is true, q is so as well. Thus steering well is a necessary condition of driving well, but it is not sufficient, for one can steer well but drive badly for other reasons. Confusion may result if the distinction is not heeded. For example, the statement that A causes B may be interpreted to mean that A is itself a sufficient condition for B, or that it is only a necessary condition for B, or is perhaps a necessary part of a total sufficient condition. Lists of conditions to be met for satisfying some administrative or legal requirement frequently attempt to give individually necessary and jointly sufficient sets of conditions.