Perhaps this philosophical _coup d'etat _may best be understood by comparing the Northern and Southern teachings. The discredited Northern school of Shen-hsiu had preached that the road to enlightenment must be traversed "step by step," that there were in fact two stages of the mind--the first being a "false mind" which perceives the world erroneously in dualities, and the second a "true mind" which is pure and transcends all discriminations and dualities, perceiving the world simply as a unity. One proceeds from the "false mind" to the "true mind" step by step, through the suppression of erroneous thought processes by the practice of _dhyana_ or meditation, in which the mind and the senses slowly reach a state of absolute quietude. The Southern school took issue with this theory of the mind on a number of points. To begin, they said that if there really is no duality in the world, then how can the mind be divided into "false" and "true"? They argued that the answer quite simply is that there is only one mind, whose many functions are all merely expressions of single true reality. The unity of all things is the true reality; our minds are also part of this reality; and upon realizing this, you have achieved the same enlightenment experience once realized by the Buddha. There is no "false mind" and "true mind," nor is there any need for a long program of _dhyana _to slowly suppress false thoughts. All that is needed is to practice "absence of thought" and thereby intuitively to realize a simple truth: One unity pervades everything. This realization they called Buddha-mind, and it could only happen "all at once" (not "step by step"), at any time and without warning. This moment of primal realization they called "seeing into one's original nature." Although Shen-hui is somewhat vague about exactly what practice should replace meditation, the scholar Walter Liebenthal has inferred the following about Shen-hui's attitude toward "sudden enlightenment" as a replacement for meditation: "He seems to have rejected meditation in the technical sense of the word. Instead of methodical endeavors designed to promote religious progress he recommends a change of point of view leading to non-attachment. . . . Non-attachment in this case means that external objects are not allowed to catch our fancy.. . . _ [A] thing recollected is isolated, it is singled out of the whole, and is thus an illusion; for all short of the undifferentiated continuum is illusive. The senses work as usual . . . but 'no desire is aroused.' . . . This change happens suddenly, that is, it is not dependent upon preceding exertions; it can be brought about without first passing through the stages of a career. That is why it is called 'sudden awakening.' _"10 _ _