Saul Kripke, commenting on Wittgenstein’s Philosophical Investigations (his idiosyncratic understanding of Wittgenstein’s work came to be known as Kripkenstein), relates the following thought experiment: let us suppose that one has never added numbers greater than 50 before. A “bizarre sceptic” could argue that there is no hard evidence against the hypothesis that it has only ever been meant for instance, that:if x, y < 57, x “plus” y = x + yif x, y ≥ 57, x “plus” y = 5