Insight: The Three Characteristics draft
Some of the quintessential insights a meditator will experience are known in the Buddhist tradition as "the three characteristics." They are impermance, unsatisfactoriness, and no-self. These play a central role because the human mind, by default, buys into their opposites: the illusions of solidity, satisfactoriness, and self. These illusions act as powerful supports for the habitual mental activities that create and maintain suffering. By investigating the three characteristics, a mind starts the process of unravelling this knot and attaining freedom.
We will consider each of them in turn but, first, a warning: for a beginner, both impermanence and unsatisfactoriness are easier to understand than no-self. The period during which a mind understands the first two characteristics beore it grasps the third can be pretty miserable. If you lose your nerve and stop investigating at this point, you can end up stagnant and worse off than if you'd never begun. This, along with what you should do if you find yourself in such a state, is covered in detail here.
Also, while you can gain a certain conceptual appreciation of these characteristics by reading the descriptions here, it is ultimately direct investigation and experience that does the damage and makes an actual difference in the quality of your life.
The Illusion of Solidity
When one starts meditating with an object like the breath, they experience the breath as "a thing." This is not a philosophical word game, of the sort "but when does a breath really, like, begin, man?" I mean this literally. When a beginner sits down, he experiences an in-breath and an out-breath as concrete experiential objects that can be meaningfully focused on.
With continued practice, this gives way to confusion. Where once there was the breath, now he notices that there are two things: there is the idea of the breath, and then there are the actual physical sensations of the breath. He realizes that before this he was focused on the idea of the breath and vows now to stay with the physical sensation of the breath. Surely, that is what is actual and real.
Practicing in this way soon gives way to more confusion. The physical sensations of the breath now seem to be there only part of the time. He starts to think maybe this breath thing isn't so solid after all. Sometimes, when his investigation is consistent, his sense of body disappears altogether. At first this is alarming, but it eventually culminates in a realization: a physical sensation itself and the knowing that contains the bodily location of that sensation are two separate things. This bodily knowing is more like an idea than what is actual and real. Undeterred, he vows to get to the bottom of this and redoubles his attention to the actual, physical breath.
This time, while observing the breath, something unsettling happens. His experience of an evolving and changing breath collapses. It is like he has been watching a film and the reel malfunctioned. Instead of a movie, he now experiences the individual frames but, unlike movie frames, these discrete bits of experience don't mean anything at all. Instead, they make him feel like he is tumbling through a dryer. He throws up his hands and gives up on looking for the actual breath. He can find no such thing.
Experience is like swiss cheese. It is full of holes. It's apparent solidity is an illusion, a misperception that can be corrected with earnest investigation.