20, In reminding the disciple 'to say nothing except what can be said', the Zen master must be able to demonstrate to any disciple 'who wanted to say something metaphysical', following Wittgenstein here, 'that he had failed to give a meaning to certain signs in his propositions'. In Zen such a demonstration might simply take the form of a curt dismissal - 'If you mention Buddha Nature here I will throw you out!' But still the master will demand that the disciple 'say something'. However, the 'saying' that is required is not an ordinary saying but a 'showing'.
Someone might object here that it is difficult to accept that there is an analogy between Wittgenstein's method and that of the Zen master. For whereas Wittgenstein is at pains to avoid saying what cannot be said - or to point out the nonsensicality of all attempts to say the unsayable - Zen, with its nonsensical koans, insists on saying what cannot be said - that is, insists on speaking nonsense - in order to effect a switch in the disciple to a rejection of what cannot be said. In response, it needs to be stressed that Zen does not reject what cannot be said. What Zen rejects is each and every attempt to say what cannot be said. Moreover, the nonsensical character of koan language is only apparent. Once the grammar of this language-game has been mastered, the nonsensical appearance of its language is seen through.