Compare the following passages which come from two individuals who lived in different times and places: Huang Po, a zen master who lived during the Tang dynasty; and Dionysius the Areopagite, a Neo-Platonist who lived around the fifth century C.E. in Syria:
“All the Buddhas and all sentient beings are nothing but the One Mind, beside which nothing exists. This Mind, which is without beginning, is unborn and indestructible. It is not green nor yellow, and has neither form nor appearance. It does not belong to the categories of things which exist or do not exist, nor can it be thought of in terms of new or old. It is neither long nor short, big nor small, for it transcends all limits, measures, names, traces and comparisons. It is that which you see before you — begin to reason about it and you at once fall into error.”
—The Zen Teaching of Huang Po (translated from the Chinese by John Blofeld)
“Once more, ascending yet higher we maintain that It is not soul, or mind, or endowed with the faculty of imagination, conjecture, reason, or understanding; nor is It any act of reason or understanding; nor can It be described by the reason or perceived by the understanding, since It is not number, or order, or greatness, or littleness, or equality, or inequality, and since It is not immovable nor in motion, or at rest, and has no power, and is not power or light, and does not live, and is not life; nor is It personal essence, or eternity, or time…nor does It belong to the category of non-existence or to that of existence…nor can reason reason attain to It to name It or to know It…”
–Dionysius the Areopagite, The Mystical Theology, V (translated from the Greek by C. E. Rolt)
No matter the label we apply to what is under discussion here it should be clear that both individuals are talking about the exactly the same thing.
Huang Po, like many Zen Buddhists before him, makes use of the idea of mind, because, unlike the brain which occupies a location in space, our mind is not something that we can point to. But keep in mind (haha) that this is simply an expedient: it’s very clear from Huang Po’s text that what he’s talking about can’t actually be talked about, except by saying what it isn’t.
Dionysius says that it is the first cause, but likewise goes on to tell us what it is not. The lists of nots in both cases is quite long, and really encompasses everything that we’re familiar with on a daily basis: things that come to us by way of our five senses, and the mental images we form thereupon. This stripping away of ideas acquired a technical, Latin name in Medieval Europe: the via negativa, or “negative way”.
Both of the passages above are attempting to describe reality as it really is, and not as it appears to us from our limited point of view. But unlike philosophers who describe what reality is by using affirmative assertions (e.g. Paremenides who said that everything is one, or Heraklitus who described everything as change) Huang Po and Dionysius challenge us not to use familiar concepts because, even though they can be be a good starting point, they can become a barrier that needs to be transcended.
But another reason for using the via negativa is because it has a practical component in meditation, especially forms of meditation that seek to quiet the mind, and purge it of its verbal behavior. By meditating in this manner, by “cutting off the streams” of verbal thought (as many Zen masters are fond of saying) we allow the mind to exist in a more open state, in order to grasp experientially a state of mind beyond words — a state where it is possible to “grasp” the truth of what the words above are pointing to.