““Whatever is true is true, but not all truths are necessary truths. It is true that adding two pebbles to two pebbles makes four pebbles; but adding two drops of water to two drops can make one pool (Piaget, 1967d, p. 582). What this means is that the action of adding actual objects together can have alternative outcomes; the sum of adding two and two can be other than four – that is a real possibility, and no contradiction arises from this.””
