“…the captain of a ship has to cross straits he does not know and does not have a chart for nor navigational help such as a beacon, etc. on a stormy dark night. In the circumstances only two things are possible: Either he sails into a cliff and loses his ship and his life: in the last moment of his life he realizes that the reality of the straits was not as he imagined and his course did not correspond with the actuality of the straits. Or he reaches open sea: then he knows only that his course was accurate but no more. He does not know whether there could have been easier, shorter crossings than the one he blindly chose. And he does not know what the real condition of the straits was….”
 von Glasersfeld, E. 1995. Radical Constructivism: A Way of Knowing and Learning. Falmer Press: London.