At bottom, the shifting nature of reality defies all categories, even here, now, and stuff. (Matter, Einstein showed, is really only a form of energy.) A mind—its consciousness and sanity—is a program built of concepts, some of them acquired from our genetics (babies fear heights and snakes, but grasp basic language concepts), some from our cultural conditioning, and some that each of us has built up by spotting patterns in banks of memories gathered from our own experiences.

The deepest form of oneself, of I, is a program that runs on brain tissue and is constantly reviewing sense data, trying to decide whether they signify hazard or opportunity or are just more familiar, non-threatening, non-promising, background noise. A mind is any program that looks for patterns in data and shows a persistent inclination to do so and then to use that data to navigate itself and its hardware safely through the hazards of physical reality.

But sanity is a construct, and like any construct it can be deconstructed. Actually, the whole worldview called “deconstructionism” is an idea that deserves a bit of digression here.

If the basic operating system of a human mind, that is, its sanity, is deconstructed, as sometimes happens when a person’s perceptions are rendered incoherent by drugs or sensory deprivation or mental illness, his interactions with real-world events begin to go beyond his ability to sort and respond. Then he has a “nervous breakdown.”

Real deconstruction of a human’s mindset—that is, the set of programs that a person uses to organize his perceptions of reality— is a phenomenon that can happen, but it is not much like the deconstructionists’ way of analyzing human thinking or of interpreting works of literature and art. (Deconstruction reaches its most abstract, unintelligible heights when a critic is analyzing a work of literature.) But it is, in reality, a frivolous activity, an empty word game. 

Deconstructionism as a philosophy is a kind of playing at mental illness. It is correct in asserting that every sane human cognition is part of a “text” and can be deconstructed into its constituent parts, most of which are culturally imprinted and so can be shown to be culturally biased. But complete deconstruction of any “text”—or context, to put it more accurately—would require the deconstructer to deconstruct the components and then the components of the components. What in her whole mindset and her culture's way of socializing her into that mindset has led her to talk and act like this, i.e. to play this word game? What in her education or upbringing so far has led her to this activity?  

She would have to continue until she had deconstructed her own mind as part of the text being analyzed. In short, she would need to go mad.

Deconstructionists are too cautious to use their method to its logical limit. Mental illness, they well know, is not clever, sophisticated, illuminating, or even logical.

Furthermore, past all these considerations, we can choose to adopt Bayesianism as our worldview; we can accept that we may never fully know reality as it is yet still believe that we can get ever closer to understanding it by repeated iterations of the scientific method. I can not believe in “truth” and still believe that courage, thinking, hard work, and cooperation can make our lives healthier and safer than they are now. The fact that I can’t grasp everything does not mean that I must believe in nothing.