We must return to the question of truth, because it has not been satisfactorily addressed.
The goal of anything must be to separate out arbitrary human constructs from actual reality—like separating fictitious things such as “the stamp collection” away from the real thing, “stamps”—but this is built on the bedrock that “actual reality” is an objectively real thing, for which the only methods we have of measuring and ascertaining the realness of are our own subjective senses and biased perspectives. The argument can certainly be made that reality itself is an arbitrary human construct.
This is a statement of fact, at least according to the perceptions of my perception. It could very well be that I am a brain floating in a jar somewhere, imagining all of this; it could also be that I am a god, and this is the reality that I have created for myself. There are limitless possibilities, but it would be unfair to simply assume that my perceptions are reliable, that I’m not a floating head in a jar. Occam’s Razor would suggest that my perceptions are real, but we must be weary of discarding possibilities simply because they are inconvenient.
Are my perceptions real? That would be the follow-up question, because there is absolutely no doubt that I perceive. You can doubt that I perceive, just as I can doubt that you perceive, but I cannot doubt that I perceive because if I did not perceive then I would not be able to state that I perceive. I perceive that my perceptions are real, but I could not perceive anything else, even if they weren’t, because the very mechanism that allows me to perceive is the very mechanism that tells me that my perceptions are real.
There are only two possibilities: that my perceptions are reliable, and that my perceptions are not reliable. There is no criteria with which I can distinguish between the two, by which I can determine whether my perceptions are reliable or not. One might say that I could measure, that I can hold the ruler in my hand and measure the length of a desk to determine that it is the length that I perceive it to be, but I perceive myself holding the ruler and measuring the desk. If my perceptions are not reliable, then the same thing that makes my determination of the desk’s very existence unreliable will make my holding the ruler and measurement of the desk unreliable.
If I am insane and imagining a desk and reality where there isn’t one, then why wouldn’t that insanity—that unreliability of perception—also include my imagining a ruler in my hand? It might even include some figment of my imagination coming and informing me that reality is definitely real. The man who believes he is Abraham Lincoln, after all, doesn’t know that he is an insane man believing himself to be Lincoln; all of his perceptions misinform him and reinforce that belief; a nurse giving him meds is perceived as a congressional official of the nineteenth century.
Any method of measurement, logic, or emotion that we would use to determine whether or not our perceptions are reliable will also, by its very nature, be contingent upon and subject to the same question of reliability. It becomes a moot point, a fun intellectual exercise, and a question of jaw-dropping wonder, but it cannot hold any further value. The question is impossible to answer, a red herring.
I cannot measure a piece of wood and objectively give its measurement if the ruler with which I measure the wood cannot be demonstrated to be reliable. And if the only way that I can demonstrate the reliability of the ruler is with the ruler itself, then it a red herring to even try to figure out. If the ruler is reliable, then it will measure itself as reliable. If the ruler is not reliable, then it might measure itself as reliable anyway. If the ruler has any sense of self-preservation at all, then regardless of its reliability the ruler would measure itself as reliable, since a ruler that measures itself as unreliable–in addition to being reliable enough to give us the answer that it is unreliable–would be discarded by anyone who wanted to measure anything.
Here we hit upon an interesting feature of logic. If the ruler is unreliable and measures itself as unreliable, then isn’t the ruler, by definition, reliable? In this analogy, we could actually measure things multiple times, but we can see how this doesn’t hold true of reality. We get one measurement of the ruler, one test to determine whether it is reliable. If the ruler is reliable, then it will affirm that, because that is the nature of reliability. If the ruler is not reliable, it would return that it is reliable. If the ruler is not reliable, it cannot return that it is unreliable, because doing so would make it truthful—reliable.
In other words, that the ruler is unreliable is the one result we cannot get, regardless of whether the ruler is reliable or not; by its very nature, the ruler must always insist that it is reliable.