The ideas of instantaneity and gradation in the realisation of the truth of Zen originally comes from the _Laṅkāvatāra_ (Nanjo’s edition, p. 55), where this distinction is made in regard to cleansing one’s mind of its stream of ideas and images. According to the Sutra, this cleansing is in one sense gradual but in another abrupt or instantaneous. When it is regarded as like the ripening of a fruit, the modelling of a vessel, the growing of a plant, or the mastering of an art, which takes place gradually and in time, it is an act of gradual process: but when it is comparable to a mirror reflecting objects, or to the Ālaya reproducing all mental images, the cleansing of mind takes place instantaneously. Thus the Sutra recognises the two types of minds: with some the cleansing to a state of enlightenment can be obtained gradually after a long practice of meditation, perhaps through many a successive life; but to others it may come all of a sudden, even without previously conscious efforts. The division of the two schools as regards the abrupt realisation of enlightenment is based not only on the statements in the Sutra but ultimately on facts of psychology. The point at issue however was not a question of time; whether enlightenment took place as an act of one moment or not, ceased to concern them; for the difference now developed into that of their general philosophical attitude and outlook towards the fact of enlightenment itself. The question of physical time has thus turned into that of psychology in its more profound aspect. When process is emphasised, the end is forgotten, and process itself comes to be identified with end. When a disciple of Shên-hsiu came to Hui-nêng to be instructed in Zen, he asked what was the teaching of Shên-hsiu, and the disciple informed him thus: “My master usually teaches us to stop the working of our minds and to sit quietly in meditation for a long time at a stretch, without lying down.” To this Hui-nêng responded: “To stop the working of mind and to sit quietly in meditation is a disease and not Zen, and there is no profit whatever to be gained from a long sitting.” Then he gave him the following gāthā: “While living, one sits up and lies not, When dead, one lies and sits not; A set of ill-smelling skeleton! What is the use of toiling and moiling?”[4.55] This shows exactly where Hui-nêng stands in relation to his rival Shên-hsiu who is so taken up with the practical details of the process of Zen. Those two gāthās inscribed on the monastery wall at Yellow-plum Mountain while they were yet under the tutorship of Hung-jên, are eloquent enough to bring out the characteristic features of the two schools.[f101]