Suppose that Jimmy is visiting at his friend, Tim. He wanted to make sure that Tim is in the study room and hence went to see for himself. In the study room, he sees a boy with the same build; same clothes and same face and concludes that Tim is indeed in the study room. However, unknown to Jimmy, he had seen Tims twin brother and Tim was indeed in the room, hiding behind the door. Hence, Jimmys belief is justified and true, yet he did not have knowledge of Tims presence in the room. I feel that Gettier problems are generally made up of two unfortunate incidents.
Firstly, there is this unlucky accident where the belief even though supported by strong justification, remains false (where the unlucky case that Tim have a twin brother. ) Secondly, unknown to the observer, in some unfortunate twist, the belief happens to be true (Tim happens to be hiding behind the door. ) There is this close but not inviolable relationship between truth and justification and when there is a difference between what is true and the evidence that the justification offer, a Gettier problem is thus formed.
Gettier problems argue that if knowledge is solely justified true belief, then there must not be any cases of justified true belief that are not knowledge. Yet, but Gettier problems are counterexamples of justified true belief without being knowledge. Hence, one is to either refuse that Gettier problems are justified true beliefs, or accept that Gettier problems are indeed knowledge. However, I feel that Gettier problems does not necessary disprove the tripartite theory of knowledge as justified true belief.
For instance, if there is an assumption that happens to be true and you believe to be true with all the necessary and relevant justification provided, despite it being a flawed justification, the observer still reach a true conclusion. Hence, it is safe to say that the final belief and final knowledge remains unchanged and that the knowledge that the observer has, is a true, justified belief.
Hence, the tripartite theory of knowledge provide a sufficient definition and that even though, in certain situations where this theory is provoked, the final knowledge remains unchanged, true and justified.