From the point of view of Zen Buddhism , the “essentialist” tendency of the empirical ego is not admissible not only because it posits  everywhere “objects” as permanent substantial entities, but also, and particularly, because it posits itself, the empirical ego, as an ego-substance. It not only sticks or adheres to the external “objects” as so many irreducible realities, but it clings to its own self as an even more irreducible, self-subsistent reality This is what we have come to know as the “abiding mind ” (prasthitam cittam). And a whole world-view is built up upon the sharp opposition between the “abiding mind,” i.e., the “subject,” and its “objects ” This dichotomy of reality into subject and object, man and the external world, is the foundation of all our empirical experiences. Of course even common-sense is ready to admit that the phenomenal world, including both the external things and the personal ego, is in a state of constant flux. But it tends to see within or behind this transiency of all things some elements which remain permanently unchangeable and substantial.Thus is created an image of the world of Being as a realm of self-identical objects, even the so-called “subject” being strictly speaking in such a view nothing but one of the “objects.” It is precisely this kind of ontological view that Zen Buddhism is firmly determined to destroy once for all in order to replace it by another ontology based upon an entirely different sort of epistemology.
For a better understanding of the world-view which is peculiar to the supra-consciousness , let us, first, take up the normal type of world-view which is most natural and congenial to the human mind, and analyze its inner structure at a philosophical level.
Two stages or forms may conveniently be distinguished within the confines of such a world-view. The first is typically represented by Cartesian dualism standing on the fundamental dichotomy of res cogitans and res extensa. As a philosophy, it may be described as an ontological system based on the dualistic tension between the two “substances” that are irreducible to one another. As a world-view, it may appropriately be described as one in which man, i.e., the ego, is looking at things from the outside, he himself being in the position of a spectator. He is not subjectively involved in the events that take place among various things before his own eyes. Man is here a detached  onlooker confronting a world of external objects. A whole ontological scenery is spread out before him, and he, as an independent personal “subject,” is merely enjoying the colorful view on the stage of the world.This is a view which is the farthest removed from the reality of the things as they reveal themselves to the eyes of the supra-consciousness.
The second stage may conveniently be represented by the Heideggerian idea of the “being-within-the-world,” particularly in the state of the ontological Verfallenheit. Unlike the situation we have just observed in the first stage of the dichotomous world-view, man is here subjectively, vitally involved in the destiny of the things surrounding him. Instead of remaining an objective spectator looking from the outside at the world as something independent of him, man, the ego, finds himself in the very midst of the world, directly affecting him and being directly affected by him. He is no longer an outsider enjoying with self-complacency what is going on on the stage of the theater. He himself is on the stage, he exists in the world, actively participating in the play, undergoing an undefinable existential anxiety which is the natural outcome of such a position.
The common-sense world-view at this second stage is far closer to Zen than the first stage.Yet, the empirical world-view, whether of the first or the second stage, is strictly speaking totally different from the Zen world-view with regard to its basic structure. For the empirical world-view is a world-view worked out by the intellect that can properly exercise its function only where there is a distinction made between ego and alter. The whole mechanism stands on the conviction, whether explicit or implicit, of the independent existence of the ego-substance which stands opposed to external substantial objects. Whether the subject be represented as being outside the world of objects or inside, this very basic Cartesian opposition is, from the standpoint of Zen, something to be demolished before man begins to see the reality of himself and of the so-called external objects.
In truth, however, even in the midst of this empirical view of the things there is hidden something like a metaphysical principle which  is, though invisible, constantly at work, ready to be realized at any moment through the human mind to transform the normal view of the world into something entirely different. This hidden principle of the metaphysico-epistemological transformation of reality is called in Buddhism tathagata -garbha, the “Womb of the absolute Reality” But in order to see the whole structure from this particular point of view, we shall have to submit it to a more detailed and more theoretical analysis . 
The epistemological relation of the ego to the object in the ordinary empirical world-view may be represented by the formula: s ➔ o, which may be read as: i see this.
In this and the following formula, be it remarked at the outset, the words written entirely with italicized small letters (like i, see, this) shall refer to things and events pertaining to the dimension of ordinary consciousness, while those written with capital letters (like I, SEE, THIS) shall refer to the dimension of supra-consciousness. And the word SEE is supposed to be a literal translation of the Chinese word chien appearing in the celebrated phrase chien hsing “seeing into ones nature”
Thus in the formula just given, the grammatical subject, s, represents the ego-consciousness of man at the level of empirical experience. It refers to the awareness of selfhood as Da-sein in the literal sense of “being-there ” as a subject in front of, or in the midst of, the objective world. The i is here an independently subsistent ego-substance. As long as the empirical ego remains on the empirical dimension, it is conscious of itself only as being there as an independent center of all its perceptions, thinkings and bodily actions. It has no awareness at all of its being something more than that.
However, from the viewpoint of Zen which intuits everywhere and in everything the act of the tathagata-garbha, the “Womb of the absolute Reality,”  there is perceivable, behind each individual i, Something whose activity may be expressed by the formula (S ➜ ) or (I SEE) the brackets indicating that this activity is still hidden at the empirical level of self-consciousness. Thus the structure of the empirical ego, s, in reality, that is, seen with the eye of Zen, must properly be represented by the formula:
(S ➔) s
or: (I SEE) myself.
As we shall see later in more detail, the empirical ego, s, can be the real center of all its activities simply because that hidden Principle, (S ➔), is constantly functioning through s.The empirical ego can be selfhood only because every subjective movement it makes is in truth the actualization here and now of that Something which is the real Selfhood. The nature of the activity of (I SEE) may best be understood when it is put side by side with its Islamic parallel presented by irfan type of philosophy which finds an explicit reference to the same kind of situation in the words of God in the Qur’än: “It was not you who threw when you did throw; it was (in reality) God who threw.”  The important point, however, is that this state of affairs is at this level still completely hidden to, and remains unnoticed by, the empirical ego. The latter sees itself alone; it is totally unaware of the part between the brackets: (S ➜).
Exactly the same applies to the “objective” side of the epistemological relation (represented in the above-given formula by the small o). Here again the empirical ego has the awareness only of the presence of “things.’’The latter appear to the ego as self-subsistent entities that exist independently of itself. They appear as substances qualified by various properties, and as such they stand opposed to the  perceiving subject which sees them from the outside. Viewed from the standpoint of the above-mentioned prajna , the “transcendental cognition,” however, a thing takes its rise as this or that thing before the eyes of the empirical ego simply by virtue of the activity of that very same Something, (S ➔), which, as we have seen, establishes the ego as an ego. A thing, o, comes to be established as the thing, o, itself as a concrete actualization of that Something. It is properly to be understood as a self-manifesting form of the same tathagata-gavbha, the “Womb of the absolute Reality” which is eternally and permanently active through all the phenomenal forms of the things. 
Thus the formula representing the inner structure of o must assume a more analytic form:
(S ➔) o
or: (I See) this.
This new formula is so designed as to indicate that here, too, o is the only thing which is externally manifested, but that behind this phenomenal form there lies hidden the activity of (S ➔), of which the empirical ego is still unaware.
In this way, the so-called subject-object relationship or the whole epistemological process by which a (seemingly) self-subsistent ego-substance perceives a (seemingly) self-subsistent object-substance, and which we have initially represented by the formula S ➔ o, must, if given in its fully developed form, be somewhat like this:
In this last formulation, the s or the empirical ego, which is but a particular actualization of (S ➔), is put into a special active-passive relation with the “object” or o, which is also a particular actualization of the same (S ➔). And the whole process is to be understood as a concrete actualization of I SEE, or S ➔ without brackets. But even in the I SEE there is still noticeable a faint lingering trace of ego-consciousness. Zen emphatically requires that even such an amount of ego-consciousness should be erased from the mind, so that the whole thing be ultimately reduced to the simple act of SEE pure and simple. The word “no-mind” to which reference has been made refers precisely to the pure act of SEE in the state of an immediate and direct actualization, that is, the eternal Verb SEE without brackets.
We now begin to notice that the reality of what has been expressed by the formula: i see this, is of an extremely complicated structure at least when described analytically from the viewpoint of the empirical ego. The real metaphysico-epistemological situation which is covertly and implicitly indicated by the formula s ➔ o, turns out to be something entirely different from what we usually understand from the outward grammatical structure of the sentence. And the primary or most elementary aim of Zen Buddhism with regard to those who, being locked up in the magic circle of ontological dichotomy, cannot see beyond the surface meaning of s ➔ o or i see this as suggested by its syntactic structure (“subject” ➔ “act” ➔ “object”), consists in attempting to break the spell of dualism and remove it from their minds, so that they might stand immediately face to face with what we have symbolically designated by the Verb SEE.
We may do well to recall at this point that Buddhism in general stands philosophically on the concept of pratityasamutpada (J.: engi) i.e., the idea that everything comes into being and exists as what it is by virtue of the infinite number of relations it bears to other things, each one of these “other things” owing again its seemingly self-subsistent existence to other things. Buddhism in this respect is philosophically a system based upon the category of relatio , in contrast to, say, the Platonic-Aristotelian system which is based on the category  of substantia.
A philosophical system which stands upon the category of substantia and which recognizes in substances the most basic ontological elements, almost inevitably tends to assume the form of essentialism.
What is meant by essentialism has roughly been outlined in an earlier context. Just to recapitulate the gist of the essentialist argument for the purpose of elucidating, by contrast, the nature of the position taken by Zen Buddhism, we might remark that the essentialist position sees on both the “subjective” and “objective” sides of the s ➔ o type of situation self-subsistent substances, the boundaries of each of which are inalterably fixed and determined by its “essence ” Here o, say, an apple, is a self-subsistent substance with a more or less strictly delimited ontological sphere, the delimitation being supplied by its own “essence,” i.e., apple-ness. In the same manner, the ego which, as the subject, perceives the apple is an equally self-subsistent substance furnished with an “essence” which, in this case, happens to be its I-ness. Zen Buddhism summarizes the essentialist view through the succinct dictum: “Mountain is mountain, and river is river”.
The position of pratityasamutpada stands definitely against this view. Such a view, Buddhism asserts, does nothing other than reflect the phenomenal surface of reality. According to the Buddhist view, it is not the case that there does exist in the external world a substance with a certain number of qualities, called “apple.” The truth is rather that Something phenomenally appears to the subject as an “apple.” The phenomenal appearance of the “apple” as an “apple” depends upon a certain positive attitude on the part of the subject. Conversely, however, the very fact that “apple” phenomenally appears as such to his eyes, establishes man as the perceiving ego. Zen describes this reciprocal relationship or determination between the subject and the object by saying:“Man sees the mountain; the mountain sees man”
The reality in the true sense of the word, therefore, is Something lying behind both the subject and object and making each of them emerge in its particular form, this as the subject and that as the object. 
The ultimate principle governing the whole structure is Something which runs through the subject-object relationship, and which makes possible the very relationship to be actualized. It is this all-pervading, active principle that we want to indicate by the formula S ➔, or rather in its ultimate form, the Verb SEE.
But again, the word “something” or “(ultimate) principle” must not mislead one into thinking that there be behind the veils of phenomena some metaphysical, supra-sensible Substance governing the mechanism of the phenomenal world. For there is, according to Zen, in reality nothing beyond, or other than, the phenomenal world. Zen does not admit the existence of a transcendental, supra-sensible order of things, which would subsist apart from the sensible world. The only point Zen Buddhism makes about this problem is that the phenomenal world is not just the sensible order of things as it appears to the ordinary empirical ego; that, rather, the phenomenal world as it discloses itself to the Zen consciousness is charged with a peculiar kind of dynamic power which may conveniently be indicated by the Verb SEE.
Thus what is meant by the SEE is not an absolute, transcendental Entity which in itself might be something keeping itself completely aloof from the phenomenal things. Rather, what is really meant thereby in Zen Buddhism is a dynamic field of power in its entirety and wholeness, an entire field which is neither exclusively subjective nor exclusively objective, but comprehending both the subject and the object in a peculiar state prior to its being bifurcated into these two terms.The verbal form itself of SEE may, at least vaguely, be suggestive of the fact that, instead of being a thing, be it an “absolute” thing or be it a “transcendental” substance, it is an actus charging an entire field with its dynamic energy. In terms of the previously introduced basic formula we might say that the whole process of i see this is itself the field of the Act of SEE. The real meaning of this statement, however, will be made clear only by our analyzing more in detail the basic inner structure of this dynamic field. That will be our task in the following pages.