Philosophy is infamous for producing arguments that no one can accept. Particularly, in epistemology, we come across arguments for skepticism that go like this:
(1) I do not know that I am not a Brain-in-a-vat (BIV).
(2) If I do not know that I am not a BIV, then I do not know if I have hands.
(3) Therefore, I do not know that I have hands.
For all we know, reality as we experience it could just be the result of the machinations of some supercomputer devised by aliens to feed our brains sensory datum. We have no way to tell if we are actually existing as embodied individuals moving about in our daily lives going to work, eating food, and paying our taxes or existing as brains floating in a cylinder of nutrients hooked up to a Matrix-style reality generator. Naturally, we are quite resistant to the conclusion of the BIV argument. As it turns out, however, it is quite a hard argument to refute. The logic is valid, and the premises seem plausible. The question, then, is how to counter it.
G.E. Moore is perhaps the most famous opponent of this kind of argument, and offers the following:
I can prove now, for instance, that two human hands exist. How? By holding up my two hands, and saying, as I make a certain gesture with the right hand, “Here is one hand” and adding, as I make a certain gesture with the left, “and here is another.” And if, by doing this, I have proved ipso facto the existence of external things…
So there you have it! Wasn’t that easy? It appears to go like this:
(1) I know that I have hands.
(2) If I don’t know that I’m not a BIV, then I don’t know that I have hands.
(3) Therefore, I know that I am not a BIV.
It is no surprise that the skeptic is not impressed by this, as it seems to just beg the question. But so what? Moore’s point was that any argument put forward to undermine our knowledge of having hands should just, in principle, be rejected. These are special kinds of facts, and after decades of reflection by hundreds of philosophers, they have come to be referred to as “Moorean facts.”
Another example comes from the ancient Greek philosopher Zeno who famously argued that there is no such thing as motion. Consider an arrow in flight. Naturally, we think of it as moving from one spatiotemporal location to another. However, when we consider each instant of time by itself—say a solitary slice of time—we see that the arrow is anchored in one location and not another. In the subsequent time slice we see it in a slightly different location and so on. Thus, like a film strip, the objects “moves” by each snapshot of time appearing before our mind in a successive sequence. Since things do not move in a single slice of time, our sense of motion is illusory, and therefore impossible.
Commenting on this argument, the famous metaphysician David Armstrong said,
It is a very fundamental part of the Moorean corpus that there is motion. Things move. Perhaps we have still not, after two and a half thousand years, got to the full bottom of Zeno’s brilliant arguments against the existence of motion . . . But certainly Zeno should not persuade us that things do not move. Neither should anybody else.
So it seems there is a special set of facts that no one can reasonably deny. These so-called “Moorean facts “have a special kind of standing in our set of beliefs where it is particularly resistant to being rationally undermined. If an argument comes along and casts doubt upon its standing, the argument is dismissed as haphazard, petulant, or even preposterous. Even if we can’t point to the error in the reasoning of the argument, we still reject it. Being charged with begging the question will not bother us. We insist on knowing things as things we cannot not know even if there are arguments showing them to be things we cannot know. How they come to have this place is not so easy to account for… they just do.
HT: Thomas Kelly