Abstract
After describing Wittgenstein's notion of ‘certainty’, in this article I provide four arguments to demonstrate that no certainty can be acquired at will. Specifically, I argue that, in order to assimilate a certainty, it is irrelevant whether the individual concerned has found a ground that seemingly justifies that certainty; has a given mental state; is willing to accept the certainty on the proposal of a persuader; or tries to act according to the certainty involved. Lastly, I analyse how each of these arguments is reflected in the way children acquire certainties.