forum 1, week of Jan 8, Dretske
I agree with this idea that relevant alternatives should be supported by some kind of empirical evidence. If one were to take seriously any possible alternative then there would be very little one could claim to actually know. Even a priori knowledge could be questioned if one were to believe that there was some kind of evil demon operating solely to trick them. If empirical evidence were not enough to give us true knowledge, then one would be forced to say that 'I think that' or 'It is likely that' the zebras are not painted mules. I do not think that this particular example can be dealt with by saying it is a problem of semantics. I think one can say that they literally know that the zebras are zebras by applying these standards of empirical evidence to rule out alternatives, such as painted mules.
I agree that there would be very little one could claim to actually know, IF we have to consider all possible alternatives. However, one fundamental problem is that empirical evidence may or may not be enough to give us true knowledge, depending on the notion of evidence used. Yes, there is no consensus yet on what the heavily-used concept of evidence is! Besides, what are these standards of empirical evidence that you have in mind? Are they related at all to the definition of "evidence" given by Richard Royall and Steven Goodman? (e.g., see http://www.ncbi.nlm.nih.gov/pubmed/3189634 or http://www.botany.wisc.edu/courses/botany_940/06EvidEvol/powerpoints/Evidence.pdf)