Possibility is not Probability

From Alexander Wendt's 'Constructing International Politics.' International Security, Vol. 20, No. 1. (Summer, 1995).
"Mearsheimer thinks it significant that in anarchy, states cannot be
100 per cent certain that others will not attack. Yet even in domestic
society, I can not be certain that I will be safe walking to class.
There are no guarantees in life, domestic or international, but the
fact that in anarchy war is possible does not mean 'it may at any
moment occur' (Waltz 1959). Indeed, it may be quite unlikely, as it is
in most interactions today. Possibility is not probability. Anarchy as
such is not a structural cause of anything. What matters is its social
structure, which varies across anarchies. An anarchy of friends
differs from one of enemies, one of self-help from one of collective
security, and these are all constituted by structures of shared
knowledge. Mearsheimer does not provide an argument for why this is
wrong; he simply asserts that it is" (pp. 78-9).