The Brain-In-A-Vat argument (biv), which can be traced back to Descartes as the Evil Demon Argument, is a skeptical argument which says that you don’t know that you have hands. The biv argument seeks to disprove all elements of the material world, with hands being the most basic example. The Evil Demon Argument seeks to disprove both knowledge through observation (knowledge such as: “I see my hands, so I know I have hands”) as well as knowledge through reflection (knowledge such as: “if there are ten people in a room, then there are also nine people in the same room”). The biv argument seeks only to disprove knowledge through observation and use knowledge through reflection to do so. This is the main difference between Descartes’ Evil Demon Argument and the biv argument. The biv argument goes like this:
- If you know you have hands, then you know you aren’t a biv.
- You don’t know you aren’t a biv.
- So, you don’t know you have hands.
One critique of the biv argument is Thomas Reid’s ‘same shop, same maker’ critique. The same shop, same maker critique presents the idea that there is a watch shop. In this watch shop there are watches which are made by a watch maker. This watch maker also makes and sells a machine which will scan the watches made in the shop and tell you whether the watches are trustworthy or untrustworthy. A patron purchases a watch from the shop. The patron also purchases a watch scanner. The watch scanner tells the patron that the watch they purchased is untrustworthy. The same shop, same maker critique goes like this:
- It would be a mistake to be convinced by the machine’s verdict of untrustworthiness.
- And, if it would be a mistake to be convinced by the machine’s verdict of untrustworthiness, then it would also be a mistake to be convinced by the biv argument.
- Hence, it would be a mistake to be convinced by the biv argument.
Premise one is true. It would be a mistake to be convinced by the machine’s verdict of untrustworthy. It would be a mistake because it is just as likely that the watch scanner is at fault seeing as it was made in the same shop, and by the same maker. It would be just as reasonable, in this situation, to think that because the watch and the watch scanner disagree that the scanner must be the untrustworthy agent and that the watch is correct. It seems arbitrary to select one to believe and one to blame based on the available knowledge.
The same shop, same maker critique rejects the skeptical biv argument that knowledge based on observation (that you know you have hands) can be disproved by knowledge based on reflection (that you don’t know you aren’t a biv), and thus, that you cannot prove that the material world exists. It rejects this argument because, like in the same shop, same maker critique, the skeptic faces an arbitrary decision of selecting one type of knowledge to prove the other is untrustworthy. If you have two faculties, and they have both come from the same place, how can you reasonably think that one of these faculties is correct while the other is not? If the patron is mistaken, then the skeptic must also be mistaken. This means that premise two is true by way of an analogy.
This is a good critique. It is good because the same shop, same maker critique does not directly engage the premises, or content, of the biv argument. It escapes the typical issues of proving that one does indeed know, to whatever standards of knowledge one may have, that they are not a biv. The same shop, same maker argument instead refutes the methodology upon which the biv argument stands. It refutes the idea that we can discount all knowledge obtained through observation, and by extension the material world, simply based an argument built on knowledge gained through reflection. In this way the advocate of the same shop, same maker critique does not need to prove that the material world exists, or even that you are not a biv, but only that it would not be logical to believe the biv argument based on one type of knowledge to the detriment of the other.
Additionally, a good argument should not use the arbitrary playing of favorites to convince someone of their beliefs. Being arbitrary is not being rooted in fact, but rather using the blind belief that A is superior to B simply because I deem it to be. The same shop, same maker critique does an excellent job of making the case that choosing one knowledge over another is arbitrary, and by extension, bad. The same shop, same maker argument does this by equating the arbitrary choice faced by the patron, to believe the watch or to believe the watch scanner, and the decision the skeptic faces, to believe their knowledge through reflection or their knowledge through observation. By showing that it would be wrong for the patron to be convinced that the watch is at fault, we can be adequately convinced that it would also be wrong for the skeptic to use the same flawed logic to make their argument.
