Explain how Edmund Gettier revised the tripartite theory of knowledge.

The tripartite definition of knowledge states that knowledge is justified true belief. That is, for an individual, A, to be able to claim that she knows that p is true, p must be true, A must believe that p is true, , and A must be justified in believing that p. This definition held strong since Plato, but it was only challenged in 1963 by Edmund Gettier.Gettier presented cases in which an individual had a justified, true belief, yet she would not be able to claim that she has knowledge of something. For example, as I am looking outside my window, I see what I believe to be my cat sitting on the grass. Thus, I deduce that the proposition "My cat is sitting on the grass outside" is true. However, the cat that I saw is someone else's cat which is very similar to mine. Unbeknownst to me, however, my cat actually is sitting on the grass outside, somewhere where I cannot see it. This fact, accidentally, makes my belief true. Therefore, I formed the belief that my cat is sitting on the grass outside on false grounds. Even though I had a justified, true belief, I cannot claim to have knowledge of the fact that my cat is sitting on the grass outside, as it is only by accident that I can claim to know that. Hence, with his paper, Gettier demonstrated that the tripartite theory of knowledge is not sufficient for knowledge and a fourth component needs to be added. He did not aim to add the fourth component himself, but left it open for other philosophers to do so.