One of the first things students of Ch'an are faced with is the fierce rejection of dualistic thinking. Without relying on scriptures, dogmas or any other teachings, Ch'an school of Buddhism purports to transmit its teachings in a direct manner (i.e. "directly pointing to the essence"). Admittedly, this is difficult to imagine or explain, because the very acts of imagining and explaining cannot but incorporate the exercise in dualistic thinking. As soon as that happens, the conditions for the transmission are broken, and the time and energy have been wasted. The closest that one can get to actually enveloping it in some form of dualistic thinking is as is portrayed in the following aphorism: two friends were passing their time talking about various things, when one of them mentioned that his favorite fruit is banana. "Banana? What is that?" asked the other person. "You mean you have never seen a banana or heard of it?" replied the first person, quite surprised. "No, why?" was the other person's calm reply. "Um, nothing, I just find it very odd..." murmured the first person. "Well, could you please enlighten me as to what on earth is a banana?" insisted the other person. "OK, I'll try. Do you know how a plum looks like? Of course you do. Well, a banana is not even close to resembling that!"
While the above reply manages, up to a point, to cut the delusions off the other person's mind ('don't think that a banana is something similar to any of the fruit you are familiar with'), it doesn't even hint upon what a banana actually is. In many of the Ch'an elaborations, we mostly find pointers that elucidate what the reality is not. And, in a nutshell, Ch'an masters are adamant that the ultimate truth and reality are not anything dualistic.
Logically, one is led to conclude that the ultimate reality is then monistic. But here we are entering a very dangerous and slippery terrain. We may think that if we somehow manage to resolve the tensions that abide in any dualistic constructs (clean/dirty, alive/dead, and so on), and enthrone such resolution on some sort of the monistic pedestal, that we have then reached the final truth, the ultimate realization. Of course, as is notoriously known from the vast body of preserved Ch'an and Zen literature, all we have managed to accomplish thus is to get the proverbial thirty blows from the master. It would appear that truly awakened teachers are invariably adamant that such monistic proclivity in our understanding is a very dangerous deviation from the correct path of liberation. Why is that so?
As rational beings, we are inclined toward resolving all the inconsistencies and tensions found in the perceived reality by employing the "middle ground" integration of the extremes. We have already discussed the phenomenon of making compromises and truces with reality; the same considerations apply here. To believe that the problem of good and evil, for example, is once and for all solved by introducing the concept of the highest monade (i.e. the monistic God), which is the creator of both extremes, and is therefore the ultimate source that is able to justify such things, is in every respect very infantile, to say the least. Why is this untenable? The underlying assumption (that the highest monade has the power to create dual extremes, and has therefore the power to resolve them as well) is based on the tacit belief that the monade (the monistic, noumenal godhead) is in every respect superior to its creations. It stands above them, and it can manipulate them. It cannot, under any circumstances, be manipulated by its creation.
Thus explained, this monism falls into the category of the horizontal monism. It is a monism as opposed to dualism. The final monade, the one that is the superior metaphysical source, as well as being the ultimate destination of all the manifested dualistic principles and phenomena, can only be defined and can only exist in relation to the dualistic manifestations. Remove the good and evil pair of opposites (or the life and death pair, or any other for that matter) from the picture, and is there a place left where the god can appear? Similarly, the Absolute can only be defined in terms of its relation to the Relative. And if the Absolute is relative to the Relative, and cannot be established on its own, than it is not really the Absolute, but merely the Relative, is it not?
The horizontal monism is obviously then an inferior form of monism. It is the monism we arrive at when we stop short, when we give in to the temptation to jump at the conclusion too early in the game. When we say: "yes, there is a problem of life and death, among other grave problems, and it seems like it cannot be untangled; but there is also the Absolute, and if we can only learn how to reach the Absolute, all the problems will get resolved in a blink of an eye", we have fallen the victims of the inferior, or horizontal monism. We may believe that this horizontal monism (the Absolute) will save us from the terror of the dualistic world, but our hopes are poorly founded -- the dualism remains, it is carried over when we pass to the other shore, so to speak, only this time it is much more venomous, being concealed and not immediately visible. The dualism contained in the horizontal monism is a very subtle one. It is the implied dualism between the supposed non-dual (the Absolute) and the dual (the Relative). It is much more difficult to liberate ourselves from such a formidable "cave of phantoms".
Ch'an masters warn us very openly about the dangers of such half-baked understanding when they say:
Continuing our discussion in a dualistic vein, we must now conclude that, if there is a horizontal (inferior) monism, there must also be a vertical (or, superior) monism. This is, indeed, true, and if we only remember the Ch'an dictum of penetrating through and transcending whatever it is we are working on, it will be easy to understand what this vertical monism is all about. In order to reach the level of vertical monism, we must simply go beyond the horizontal monism. And, similar to the conclusions we've reached regarding the vertical dualism, vertical monism also deals with different levels of abstraction. In horizontal monism, the proposed Absolute (the ultimate monad) revealed itself as being at the same level of abstraction as its defining counterpoint -- the Relative. This interplay at the same level of abstraction has rendered the inferior type of monism with all the attached baggage of wishful thinking and other byproducts of everyday sentimentality.
To liberate ourselves from this mess, we can look into some pointers left by people who have already traversed the same path. For instance, there is a famous Ch'an riddle:
The "all things return to one; to what
does the one return?" riddle points to the situation where the one (the
monad) returns to the state where it is meaningless to discuss the presence
or absence of such qualities as oneness, manifoldness, and
duality. It is now at a different level of abstraction from the
position of the one that was merely a final destination of the myriad
things. If we may be allowed to come up with the analogy here, the horizontal
monism could be compared to the saying that all the rivers eventually return
to the ocean, while the vertical monism could be characterized as "no rivers,
no ocean". The vertical monism gives the impression of unity, although
one is compelled to ask: the unity of what? Because such unity is devoid
of any qualities and of anything that could be ascribed to it, we arrive
at an important notion of Emptiness.