25. Meditating on koans is one of the major disciplines used in Zen. Mumon Ekai, a master active in 13th century China, spoke of using koans as brickbats to batter the gate that seems to bar entry to the way of Zen. This gate might be thought of as an impulse to say the unsayable, to speak what cannot, must not, be spoken. Mumon would liken the surrender to this impulse to 'striking at the moon with a stick', or 'scratching a shoe, whereas it is the foot that itches'. That is to say, in Zen there is a clear recognition of the incommensurability between the metaphysical impulse and what it seeks to express in the form of the propositions of philosophy or, as Mumon would put it, 'other people's words'. And so Mumon warns his disciples not to confuse their 'own treasures' - their own realisation of the metaphysical - with the 'things coming in through the gate', namely, the speculations of others. That is, he attempted, with the help of the cases of the ancient masters, that is, with koans, to awaken his monks to the fact that nothing, nothing at all, stood in the way of their full possession of the present moment of their daily lives. This nothing-gate-barrier was no more than a picture, a figment of the imagination, a product of conventional habits of thought. He might have pointed out to them that they were held captive by nothing but a picture. As Wittgenstein would say: 'A picture held us captive. And we could not get outside it, for it lay in our language and language seemed to repeat it to us inexorably'.
So might it not be the case that those who have difficulty in seeing that the practice of Zen is a philosophical practice are likewise held captive by a picture? And is this not a somewhat narrow and misleading picture of the nature and practice of philosophy, especially when viewed against the background of the whole history of Western philosophy? Here it would be well to recall the koan that asks: 'Why is it that a man of great strength cannot lift his legs?'