Fred Dretske's Analysis

One of the principal thesis that the author, Fred Dretske, wants to represent in his work is “to think of knowledge as an evidential state in which all relevant alternatives (to what is known) are eliminated”. Dretske in his work has developed an analysis of knowledge critiquing Unger’s argument about “skepticism”, which is a trend and philosophical doctrine that believes that truth does not exist or that the human being is unable to know if it exists. For that, he tries to understand and explain knowledge through the Contrasting Set (CS) where are “the situations that are eliminated by what is known”; and the Relevancy Set (RS) where are “the possible alternatives that a person must exclude”. Having explained this, let’s pay attention to the premises of the central argument:
P1: We know something exists when we have evidence. (S knows that P)
P2: If we have this justification, then we can eliminate all the possibilities of being wrong. (Then, Q is in the CS (of P) necessarily not –Q)
P3: This shows that having a reason or evidence to think that something is a possibility, it does not mean that is
I agree with the argument of Dretske because the author of the text is trying to explain the concept of knowledge through absolute concepts and their relevant alternatives. It could be explained further: we come to the conclusion that the absolute concepts represent a situation totally devoid of relevant things. He gives the example of "empty"… how can be evaluated the emptiness of a pocket vs. the emptiness of a football stadium? Such concepts have a relation. To explain it better, when you are “empty”, you are devoid of all the relevant things, because you do not stop to think about including that there are molecules in the air, therefore, it is not entirely "empty" but it is irrelevant when you have knowledge because you eliminate the alternatives and you uses the absolute concept of