Carl Ginet provided a well-known Gettier-style counterexample to the traditional tripartite account of knowledge – that knowledge is justified true belief. First published in Alvin Goldman’s article “Discrimination and Perceptual Knowledge”, which appeared in a 1976 volume of The Journal of Philosophy.
The example describes an individual, Henry, who sees a barn, and thus forms the propositional belief that what he sees is a barn. Henry is correct — that is, his belief is true. Because he happens to be in the countryside, and one would not normally expect that some barnlike object in the countryside would be anything other than a barn, most would agree that Henry is justified in his belief. Thus, Henry has a justified true belief that what he sees is a barn.
However, it turns out that the area in which Henry found the barn is scattered with façades of barns — that is, constructions that are meant to look like barns from a certain perspective (i.e., Henry’s), but are not, in fact, barns. In actuality, the barn that Henry found was one of a very small number of actual barns in the area, and it is by sheer luck that Henry happened to form his belief about that particular object.
The point of the barn-amidst-façades example is to provide a counterexample to the tripartite definition of knowledge that, unlike the Gettier counterexamples, does not rely on some false inference. The barn example is thus resistent to modifications to the definition of knowledge that account for inferences based on false premises.
Goldman himself admits that his previous causal theory of knowledge does not hold up to the barn example:
“My old causal analysis cannot handle the problem either. Henry’s belief that the object is a barn is caused by the presence of the barn; indeed, the causal process is a perceptual one. Nonetheless, we are not prepared to say … that Henry knows.¹