We have observed in the foregoing that the basic formula s ➜ o, or i see this, which is designed to describe schematically the epistemological relation between the perceiving subject and the object perceived, conceals in reality a far more complex mechanism than appears at first sight. For, according to the typically Buddhist analysis , at the back of s there is concealed (S ➜); at the back of o there is also (S ➜). And the whole thing, as we have observed, is ultimately to be reduced to the (outwardly) very simple but (inwardly) all-pervading and all-comprehensive act of SEE.
It often happens that this SEE, which is in Zen understanding nothing other than the absolute or ultimate Reality, makes itself felt in the mind of a man living on the empirical dimension of existence. The first symptom of the ultimate Reality breaking into the empirical dimension is observable in the fact that the man in such a situation begins to feel uneasy about the nature of the reality as he actually sees it. Although he is still completely locked up in the dichotomous world-view, he somehow begins to entertain a vague feeling that the true reality, both of himself and of the external things, must be something of an entirely different nature. He vaguely notices at the same time that he is actually undergoing all the tribulations and miseries of human existence simply because he cannot see the reality as he should. This phenomenon, of decisive importance both religiously and philosophically, is called in Chinese Buddhism fa hsin (J.: hosh-shin), meaning literally the raising of the mind, i.e., the raising of a deep and strong aspiration toward the enlightenment of Buddha. Philosophically, it is to be understood as the very first self-manifestation of the metaphysical S ➜.
Once this beginning stage is actualized, the Dasein as it is naturally given loses, subjectively as well as objectively, its seeming solidity. It is felt that the Dasein in its empirical form is not the real form of Being, that it is but a pseudo-reality. Urged by an irresistible drive pushing him from the pseudo-reality towards what he thinks to be the real reality, whatever and wherever it might be, man betakes himself to this or that way of possible salvation. Here Zen Buddhism proposes “sitting cross-legged in meditation” as the most authentic way for cultivating a special eye to see the reality as it really is in its original nakedness.
The “sitting cross-legged in meditation” is a somato-psychological posture by which the naturally centrifugal tendency of the mind might be curbed, and turned toward the opposite, i.e., centripetal, direction until finally the pseudo-ego loses itself in the realization of the true Selfhood which we have indicated by the formula S ➜.
Zen asserts that this kind of somato-psychological posture is an absolute necessity for the realization of the true Selfhood, i.e., the state of absolute subjectivity, because the real “self” is never attainable through a purely mental process, be it representation, imagination, or thinking. For it is not a mere matter of cognition .The question is not “knowing” ones own true self, but rather “becoming” it. Unless one “becomes” ones own self, however far one may proceed along the successive stages of self-cognition, the self will not turn into an absolute Selfhood. For the real self will go on receding ever further; it will forever remain an “object,” an object known or to be known.The self as a known object, to no matter how high a stage the cognition may belong, cannot by nature be pure subjectivity. In order to realize the self in a state of pure and absolute subjectivity, one has to “become” it, instead of merely “knowing” it. But in order to achieve this, the whole unity of “mind-body” — as suggested by the above-mentioned expression of D5gen — must “drop off.” The “sitting cross-legged in meditation” is, as Zen sees it, the best possible, if not the only possible, way of achieving, first, the unity of “mind-body” and then the unity itself “dropping off”
The expression:“the mind-body dropping off” means, in the more traditional Buddhist terminology, one’s experiencing with his total being the epistemologico-metaphysical state of Nothingness (Skt.: sunyata , Ch.: k’ung, J.: ku ). But the word “Nothingness” as used in Zen Buddhism must be understood in a very peculiar sense .
“Nothingness” in this context, to begin with, refers to the last and ultimate stage in the actualization of Zen consciousness , at which the self, ceasing to set itself up as an “object” for itself, “becomes” the self itself, and that so thoroughgoingly that it is no longer even its own self. It is in fact one of the most fundamental philosophical tenets of Zen Buddhism that when a thing — anything whatsoever — becomes its own self thoroughgoingly and completely, to the utmost extent of possibility, it ends by breaking through its own limit and going beyond its determinations. At this stage, A is no longer A; A is non-A. Or, to use a terminology which is peculiar to Zen, “mountain is not mountain.” However, to this statement Zen adds — and this is the most crucial point — that when a thing, by becoming its own self so thoroughgoingly breaks through its limitations and determinations, then paradoxically it is found to be its own Self in the most real and absolute sense.
This process may conveniently be described in terms of the traditional logical language in the following way.  One may note that, thus described, the logic of Zen discloses a remarkable originality which would clarify to a great extent the most characteristic form of thinking in Zen. As in the case of the traditional Aristotelian logic, the starting point is furnished by the law of identity “A is A,” which, as we have seen above, constitutes the logical basis of metaphysical essentialism.The law of identity signifies for Zen Buddhism too that a thing, whatever it be, is identical with itself. To express this empirical truth, Zen says: “Mountain is mountain.”
Thus outwardly at least, there is no difference noticeable here between the Aristotelian logical system and Zen logic. Implicitly, however, already at this initial stage Zen takes a view which considerably  differs from the Aristotelian position. For in the law of identity (A is A) Zen recognizes a characteristic sign of the self-complacency of normal bon sens. From the point of view of Zen, the formula: “A is Α,” instead of being a description of a well-grounded observation of the structure of reality, is but a logical presentation of the illusory view of reality seen through the veil of Maya , which is the natural outcome of mans casting upon each of the things of the world a narrow spotlight of the discriminating intellect.
The basic difference, however, between the ordinary type of logic and Zen logic comes out with an undeniable clarity at the next stage. For the former naturally develops the law of identity into the law of non-contradiction (A is not non A), while the latter develops it into glaring contradiction, asserting: “A is non-A” Zen refers to this contradictory stage by the dictum: “Mountain is not mountain.” It must be borne in mind, however, that when Zen makes an assertion of this kind, it does not do so in the same epistemological dimension as that of “A is A” As long as one remains at the level of “A is A,” i.e., the level of empirical experience, one would never be able to say at the same time, “A is non A,” unless one goes out of one’s mind.This fact will become evident beyond any doubt when one encounters a more strange-looking expression like: “The bridge flows on, while the river does not flow.”  Otherwise expressed, the making of an assertion of this sort presupposes on the part of the person the actualization of a total transformation of consciousness in such a way that he is thereby enabled to witness A as it “becomes” out and out A itself to such an extent that it breaks through its own A-ness, and begins to disclose to him its formless, essenceless, and “aspect”-less aspect.
Thus understood, the formula: “A is non A” will have to be more analytically paraphrased as: “A is so thoroughgoingly A itself that it is no longer A.” Metaphysically, this is the stage of chin k’ung (J.: shin ku ),  the “real Nothingness.” Here A is not A in the positive sense that it is absolutely beyond the determinations and deliminations of A-ness, that it is something infinitely more than mere A.
The third stage which immediately follows — or rather we should say: which establishes itself at the same time as — the stage of “A is non-A” is again “A is A .” That is to say, at the final stage, we apparently come back to the initial stage. “Mountain is (again) mountain.” Or, as a more popular Zen adage goes: “The flower is red, and the willow is green.” In spite of the formal identity, however, the inner structure of “A is A” is completely different in the two cases. For at the last stage “A is A” is but an abbreviated expression standing for “A is non-A; therefore it is A” The Diamond Sutra , to which reference has already been made, describes this situation by saying: “The world is not a world; therefore it deserves to be called world,” or “A thing — anything whatsoever — is not a thing; therefore it deserves to be called thing” This stage is technically known in Mahayana Buddhism as miao yu (J.: myo u), “extraordinary Being.” The Chinese word miao, meaning literally “subtle,” “extraordinary,” “miraculously good,” is intended to suggest that the world of Being is being seen or experienced here in an unusually elevated dimension, that it is not the world of Being as it is grasped by the discriminating activity of our relative intellect, although outwardly, that is, seen through the eyes of an ordinary man locked up in the limited sphere of empirical experience, it is still the same old world of ours in which “we eat when we feel hungry, drink when we feel thirsty, and lie down when we are sleepy.” For it is the common ordinary world which has once lost itself in the abyss of Nothingness and which, then, has taken rise again in its phenomenal form.