DeRose outlines an example which clearly illustrates of how knowledge ascription varies with context.
- In the first case outlined by DeRose, a man facing a long queue at the bank on a Friday leads to him and his wife deciding come back to the bank the next day, because he knows without checking or asking that the bank opens on a Saturday.
- In the second case outlined in DeRose's, in another context facing the same length of queue as in the first example, he checks to see if the bank will be open tomorrow, because he has a very important cheque to pay in.
Both cases are objectively the same with the sole exception being the importance of paying the cheque in the second situation is much greater in the second case. Knowing whether the bank is open on Saturday for DeRose, simply depends on the importance of paying the cheque into the bank. Though an invariantist will state that he either does or doesn't know that the bank is open on Saturday, regardless of the importance of the cheque. While the contextualist contends that the conditions for knowledge ascription must change with context, otherwise the conditions required for knowledge will be unrealistically high. “The contexts of my utterances in the two cases make it easier for a knowledge attribution in Case A than in Case B” (DeRose).
Radical sceptics have come up with numerous radical scenarios that seem to deny the possibility of any knowledge at all. Arguments including Dreaming argument, Descartes Evil Demon and the famous scenario that we could be no more than brains. One the key aims of contextualism is to undermine this radical skepticism or at the very least defuse it. An recent example from contextualist literature has been used by both DeRose and Cohen to limit the skeptical threat to our everyday knowledge. This example has sometimes been referred to as the Zebra-Mule Paradox.
The Zebra-Mule Paradox
P= I am seeing a Zebra at the Zoo
H= Any Sceptical scenario which contradicts the empirical proposition P (One example of such a scenario would be what in fact I'm seeing is a cleverly painted mule).
DeRose and Cohen say that we can truly assert the following three things:
a). I know that P (I am seeing a Zebra)
b). I do not know that not-H
c). I know that P (that it is a zebra) only if I know that not-H (that is not a painted mule).
DeRose and Cohen both want to say that all three of the above statements are true and that only contextualists are in a position to say this. They are all true in context. Shifts in context would all a)-c) to be true. The painted mule pay be a possible alternative to him seeing an actual mule, but it is deeply questionable whether such possibility is a relevant one. In the context off everyday life, it would be bizarre to claim that he didn't know it was a zebra. As he can tell it apart from the other animals at the zoo. For the skeptical scenario to be a relevant possibility what would be required would a huge shift in context. In such a context he would not be sure that the supposed zebra he was seeing was not in fact a mule. He also knows as rational individual that if he doesn't know this, then he cannot know that it is a zebra. The knowledge of c) only comes into play when the observer becomes unsure of what they are seeing. But in a normal circumstance such a possibility isn't relative.
Contextualism has also been used to show how other forms of scepticism don't pose a real threat to our everyday knowledge. A good example of this comes in the form of the contextualist reply to Peter Unger's flatness scepticism. Due to the fact that absolute terms such as flat can never really be applied to the world as no surface is absolutely flat as there is always the possibility of their being a flatter surface. Unger say's that this also applies to the term certain, it is logically necessary that if something is certain, then there is nothing which can be more certain. This leads Unger to the conclusion that certain knowledge is quite impossible. Cohen has adapted this and shown how this doesn't represent a problem for the Contextualist. For Cohen it is true to say that objects are flat in context while denying their flat in other contexts. And we can raise or lower the standards of what counts a flat dependent on the context in question. Talking about a flat cricket pitch is very different from talking about a flat pool table.
One of the biggest criticisms of contextualism is that the arguments put forward by contextualists are ad hoc reactions devised for the sole purpose of protecting everyday knowledge against the threat of scepticism. But the contextualist approach towards knowledge seems particularly compelling as it does seem that we do lower and raise the standards of knowledge depending on the context in question.