During the course of our life, we (as humans) take for granted that we know some things about the external world. In fact, we often assume that we know a lot about the external world. We know some things about what happened yesterday, and we certainly know that the yesterday existed. We know that other minds, other than our own exist; we know that tables and chairs exist. We often assume that most knowledge is something that the regular, everyday person can know; it is not specialized for philosophers, historians or scientists. However, there are some things that we simply cannot know. Some future events, for example, are not knowable to us. And if someone claims to know these things, we are justifiably skeptical of that claim.
“While almost all of us are skeptical about some knowledge claims, skeptical arguments in philosophy typically purport to show that we do not know or are not justified in believing many of the things we originality assume we know or reasonably believe.” (quote from Lemos, 2007) Many arguments for skepticism conclude that we are unable to know anything about the external world, or that we are not justified in believing anything about the external world.
There are a variety of skeptical arguments. One of the more common versions is known as human, external world, knowledge skepticism. This kind of skepticism denies that people are able to have certain types of knowledge concerning the external world. However, knowledge skepticism does not automatically entail skepticism for justification. It is possible to hold the position that we are justified in believing certain things, but the evidence is not great enough to count as knowledge. Many of the arguments for external world knowledge skepticism come from various skeptical scenarios that epistemologists refer to as bad case scenarios. There are several arguments for human, external world knowledge skepticism, and three of them are (1) the certainty argument, (2) the infallibility argument and (3) the argument from ignorance.
One of the most important aspects of a proper understanding of external world knowledge skepticism is a proper understanding of skeptical scenarios. While they come in a variety of different forms, the popular movie, “The Matrix”, is a perfect example of a classic skeptical scenario. In the movie, the characters are all in a computer simulation run by machines, and that the humans are actually connected to a complex network of computers that create what they see as the external world. The humans in the program are deceived into thinking that what they see is real, when in reality, it is nothing more than a computer program. When the main character, Neo, is “awakened” by another person, his real body wakes up out of the computer simulation and he sees the truth for the first time. While “The Matrix” is meant to be a fictional story inspired by a classical skeptical “brain in a vat” scenario, external world knowledge skeptics take these types of situations as not only possible, but actual. But, because of our limitations as human beings, we are unable to truly know anything about the external world. Philosophers refer to these skeptical scenarios as bad case scenarios, where pervasive error reigns. These bad case scenarios are not only philosophical possibilities, but they seem to be something that may, in fact, be reality. And because of this, our proper response should be to suspend judgment on what we actually know about the external world.
When we reflect on these examples, it seems clear that our sensory experience does not guarantee that our beliefs about the external world are necessarily true. And initially, that does not really seem to matter. Lots of things are possible, but the real question should be about what is reasonable. Sure, we might be a person in a vat, and our “external world” might be generated by computers. But just asserting the possibility doesn’t give us good reasons to think that we should embrace epistemological skepticism. And that is where philosophers have posited arguments for skepticism.
One argument, called the certainty argument, is stated:
One cannot be certain about what the external world is like
One knows that p only if one is certain that p.
Therefore, one cannot know what the external world is like.
According to this argument, certainty is required for real knowledge. And if we cannot be certain about things, we cannot actually know them. Due to the nature of the skeptical scenarios, we cannot truly know that the external world that we perceive is actually there. And because we cannot be certain of the external world, we cannot, therefore, have knowledge about the external world.
The first question that can be asked of the certainty argument is, “what is meant by ‘certain’’? If certainty were required for knowledge, it would seem that we have to have an adequate understanding of certainty. Skeptical epistemologists have suggested that certainty requires that our beliefs be “maximally justified”. And, considering skeptical scenarios, it seems reasonable that we cannot be “maximally justified” about the external world. After all, we really might be in a computer simulation. This lends itself to an acceptance of the first premise of the certainty argument.
But what about the second premise? Is it really true that “One knows that p only if one is certain that p”? There are reasons to doubt this premise of the argument, and these come out just by reflection on the nature of how we understand knowledge. When we think about what we know for sure, do we really know that for certain? For example, do we really know that George Washington was the first president of the United States? Of course we do. But isn’t it possible that we might be in a skeptical scenario where that is not actually true, but just a product of the computer simulation? Sure. According to the skeptic, we would not truly know that Washington was the first president of the United States because we cannot be certain. But we do know it. This lends itself to the conclusion that the certainty argument sets up too high of a standard for knowledge. This certainty standard is clearly not something we look for when we say we know something, nor should it be.
Another argument for skepticism is known as the infallibility argument, and it goes as follows:
We are not infallible about the existence and character of the external world.
If S knows that p, then S is infallible about p.
We do not have knowledge about the existence and character of the external world.
Like the certainty argument, the first premise does not seem to be controversial, simply by nature of the skeptical scenarios. It is possible that we are radically incorrect concerning the existence and character the external world, so we can accept the first premise. Similarly to the certainly argument, the second premise is where the problem is. Is it really true that “If S knows that p, then S is infallible about p”? It would seem that this is not a correct way of looking at knowledge. The mere fact that is possible for us to be mistaken about p does not imply that we do not know that p. And in yet another way, this argument is similar to the certainty argument, because it sets up much too high of a standard for knowledge.
It also seems difficult to hold to the position that the positions of these two arguments. Both the certainty argument and the infallibility argument claim such high standards of knowledge that they seem to be self-defeating. Does the advocate of the certainty argument know that certainty is required for knowledge? Does the advocate of the infallibility argument know that we must be infallible in order to have knowledge? It doesn’t seem obvious that they can know such things, and this would therefore be another reason to reject these two arguments.
A third argument for skepticism, the argument from ignorance, is unlike the first two, because it does not presuppose remarkably high standards for knowledge. The argument goes as follows:
You know that (h) only if you know that not-(v).
But you do not know that not-(v).
Therefore, you don’t know that not (h).
Because we cannot rule out the various skeptical scenarios, it would seem that the first premise is correct. If we really are in a computer simulation, we (our real bodies, not the computer simulation) are not wearing clothes. However, in order for us to know that we are wearing clothes, we have to know that the skeptical scenario is false. And because we cannot deny the possibility that the skeptical scenarios are real, we cannot therefore know that it is false. Interestingly, this lends itself to acceptance of the second premise as well. If we really cannot rule out the skeptical scenario, it would seem that we really can not have knowledge. After all, according to this argument, in order to truly know something, you have to be able to rule out the skeptical scenarios.
There have been many responses to this argument, but there are two that are particularly compelling: (1) the moorean response, (2) the inference to the best explanation response.
Philosopher G.E. Moore takes the argument from ignorance and changes the conclusion simply by changing the second premise. Instead of “but you do not know that not-v”, Moore changed it to “you know that (h)”, so that the argument becomes an argument against skepticism. It is formally laid out as follows:
You know that (h) only if you know that not-(v).
You know that (h).
Therefore, you know that not-(v).
Considering the fact that the skeptical argument and Moore’s argument in response are both logically valid, which one are we to accept? In the skeptic’s argument, the second premise seems reasonable to accept. Moore’s response to that question is, “We are all, I think, in this strange position that we do know many things, with regard to which we know further that we must have had some evidence for them and yet we do not know how we know them” (Moore, 1925). Ultimately, many people find Moore’s response plausible, but not completely satisfactory.
And, in order to be more satisfied, philosophers have proposed the inference to the best explanation response. “The inference to the best explanation response to skepticism holds that the hypothesis that there is a material world of roughly the sort we believe there to be is the best explanation for our sense experience.” (Lemos, 2007).
As philosopher Bertrand Rusell explains,
“There is no logical impossibility in the supposition that the whole of life is a dream… But although this is not logically impossible, there is no reason whatever to suppose that it is true; and it is, in fact, a less simple hypothesis, viewed as a means of accounting for the facts of our own life, than the common-sense hypothesis that there are really objects independent of us, whose action on us causes our sensations” (Russel, 1912)
According to the advocate of the inference to the best explanation, we can reject the argument from ignorance and actually have knowledge, not because the argument is logically invalid, but because our sense experience of the external world is so well explained by the hypothesis that there is an external world before me that I know it to be true.
In general, the criticisms of the inference to the best explanation response question whether or not it can account for adequate justification. And, due to the fact that one can hold to skepticism concerning justification and reject knowledge skepticism, the inference to the best explanation response seems to be a fairly reasonable response to human external world knowledge skepticism.
Although not all the arguments for human knowledge external world skepticism have been addressed, it would seem that we have fairly good reasons to approach the skeptical, “bad-case” scenarios with a fair amount of apprehension. The arguments for external world knowledge skepticism may be convincing at first, but after analysis, there are multiple reasons why their conclusions should not be accepted.
Thanks for reading! This is a modified form of a research project I did for my undergrad epistemology class in 2013.