It's all about the deep questions.
Skepticism – The Brain in the Vat Argument: Cartesian Complications
Closing the Loopholes
In this post, I’ll go through some limitations of the argument, and how the argument may even be modified slightly in order to reach a stronger conclusion. First of all, it is clear that no skeptic conclusion can conclude that all knowledge is impossible. One example of infallible knowledge that everyone can have, famously stated by Descartes, is that he himself exists. Simply thinking about the question implies one exists to do the thinking, which directly leads into the famous quote, “I think therefore I am.” Most skeptical theses, therefore, argue against the possibility of knowledge about the external world (although recent psychological studies point to the fact that we know far less about our “internal” world than we once thought). Some further restrictions must be made to this skeptical thesis, however. Certain trivial analytic statements (statements true simply by virtue of the concepts involved) certainly cannot be included in a skeptical thesis. It is pretty easy to know, for example, that if there are bachelors, than they must all be unmarried.
So what does it mean for “someone to know nothing about the external world”? Three cases of knowledge are under the umbrella of this statement
- Any case of someone’s knowing something which entails the existence of some concrete entity outside his own mind. (Example: Someone knowing that many bachelor’s are happy since that entails the existence of at least one bachelor.)
- Any case of someone’s knowing something which entails that some concrete entity, such that it is not an anlytic or logical truth that it does not exist (outside the person’s mind), does not exist. (Example: Someone knowing that there are no flying pigs exist.)
- Any case of someone’s knowing something which entails a truth about a concrete entity, which is not an analytic or logical truth. (Example: if dolphins exist, then they are rainbow.)
That is a pretty strong skeptical position!
There are a couple of exotic cases that fall under these bullet points that do not seem to be compellingly addressed by our argument, however. Consider someone who believes that there actually is an evil scientists out there deceiving people. One thing he does know is that if there is an evil scientist messing with his brain, then it is not the case that that scientist is deceiving him into believing falsely that an evil scientist exists. Because if there were such an evil scientist, then it would be true that he existed! Therefore, according to this argument, he might as well know that an evil scientist exists (this argument doesn’t counter that belief). This suggests the use of contrast cases. If one knows that an evil scientist exists, then he would have to know that when he was born he wasn’t filled with drugs or chemicals that make him constantly fall into error about external matters, so that his beliefs are only randomly related to the external world.
The new argument may look something like this:
1. If one knows some fact about the external world, p, then one can or could know that he at least believes that p and, furthermore, that there is no evil scientist, a being other than himself, who is deceiving him into falsely believing that p, and lastly, that he was not given certain drugs at a young age which make his cognitive faculties continually fall into error in such a way that in truth, p is false.
2. In respect of anything which might be known or believed about the external world, say p, no one can our could know that he at least believes that p and that there is no evil scientist, a being other than himself, who is deceiving him into falsely believing that p, and lastly, that he was not given certain drugs at a young age which make his cognitive faculties continually fall into error in such a way that in truth, p is false.
3. In respect of anything which might be known or believed about the external world, say, that p, no one everknows that p.
There is (still) a further loophole into our skeptical argument however. One can still know certain conditional statements that this argument does not work against. Such as: If there is no evil scientist and my experiences are not just randomly related to any external things there may be, then rocks exist. However, no further complication to our argument can close all such loopholes. For the “If” part of the statement can just be added to indefinitely with every exotic skeptical case we put into our premises. We will have to be content with this minor loophole it seems.
G.E. Moore’s Common Sense Objection
Philosopher’s in the Common Sense tradition, not surprisingly, give much weight to common sense in philosophical argumentation. To them it is obviously true, that a person can know, for example, that there are rocks. Their argument would look something like this:
When pressed to say exactly which premise they reject in the skeptic’s argument, most likely they will reject premise 2. In other words, they say that they know there is no evil scientist. At this stage, the debate depends on where your intuitions fall. Personally, my intuitions fall squarely with the skeptic. It seems to me to be completely dogmatic for someone to assert that he knows that there is no such evil scientist or any other case that might put him into error. This objection fails in my eyes.