Introduction Epistemology has been a major branch in western philosophy since Descartes established his philosophical system. A significant problem in epistemology, a study for knowledge, is what are the conditions for one to possess knowledge. In Anglo-American philosophy, it is a prominent topic that impressed a number of researcher, as well as me. In the following section, I shall sketch out the analysis of knowledge in the present day. The Analysis of Knowledge The objective of the analysis of knowledge is to specify the conditions that are separately necessary and jointly sufficient for propositional knowledge: knowledge that such-and-such is the case. Propositional knowledge is distinctive from two other kinds of knowledge outside the scope of the analysis here: knowing a place or a person, and knowing how to do something. The concept of knowledge is analyzed commonly in virtue of the schema "S knows that p", where "S" refers to the knowing subject, and "p" to the known proposition. An analysis is presented in the following form: S knows that p if and only if X. X refers to a list of conditions that are separately necessary and jointly sufficient. To test whether a proposed analysis is correct, we must examine (a) whether every possible case in which the conditions are met is a case in which S knows that p, and (b) whether every possible case in which S knows that p is a case in which each of these conditions is met. The traditional analysis, which was once take for a sound one, goes as follows: S knows that P if and only if (1) P is true, (2) S believes that P, and (3) S is justified in believing that P. Condition (1), the truth condition, receives nearly universal assent. It is overwhelmingly clear that what is false cannot be known. Condition (2) and (3), though has generated some degree of discussion, in principle are accepted. Gettier's Problem In his short 1963 paper, "Is justified true belief knowledge?", Edmund L. Gettier proposed two counterexamples to the traditional analysis. In this article, Gettier intends to argue that the three sufficient and necessary conditions of knowledge, in the past firmly asserted by many, are indeed not sufficient for knowledge. That is to say, the three conditions for a proposition P do not logically make it knowledge. Gettier demonstrated that to us in the opposite way, that is, 'S knows that P' is not the necessary condition for the three statements. (That A is the sufficient condition for B is identical with that B is the necessary condition for A.) Even though the conditions above are true, S still does not know that P. thus, P is exclude from knowledge. He described two cases, in which (1), (2) and (3) are true but 'S knows that P' is false, that is, S do not know that P. In case one, Smith believes and is justified in believing that 'The man who will get the job has ten coins in his pocket', for the president assured him that Jones would get the job and he had just counted the coins in Jones's pocket. At last, Smith got the job and, unknown to him, he happened to have ten coins in his pocket. So what Smith believes is true, but Smith doesn't know it. In case two, the similar situation offers the counterexample to argue that 'S knows that P' is false when the alleged sufficient conditions is true. An Alternative Approach Above, we noted that the role of the justification condition is to ensure that the analysis does identify as knowledge a belief that is true out of luck. The lesson to be learned from the Gettier problem is that the justification condition by itself cannot ensure this. Even a justified belief, understood as a belief based on good evidence, can be true out of luck. Thus if the traditional analysis of knowledge is to exclude all cases in relation to luck, it must be amended with a suitable fourth condition, a condition that succeeds in the qualification of knowledge. --

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