 We’ll begin with a brief outline of the argument of Kripke’s sceptic. Suppose that I’ve never dealt with numbers larger than  57.[3]  (Given our finite nature and the infinitude of the natural number series, there will always in fact be such a number.) I’m asked to perform the computation ‘\(68+57\)’, and I arrive at the answer ‘125’, which I take to be right. However, a “bizarre skeptic” (Kripke 1982: 8) questions my certainty. She suggests that in the past I used ‘plus’ and ‘+’ to mean a different function, which she calls “quaddition”. Quaddition yields the same result as addition if the numbers are lower than 57, and 5 otherwise, so the correct result of the aforementioned computation is ‘5’, not ‘125’. I should answer ‘5’ if I intend to use ‘plus’ in the same way in which I have been using it in the past, or so the sceptic suggests.