Gettier and JTB. The JTB theory of knowledge seeks to give a collection of necessary and sufficient criteria for a person to be called to know something. According to the idea, if a person p has a belief b, and if b is true, and if p is justified in believing b, then p knows that b. If JTB is correct, then no human being can fail to know some truth about the world around him or her. Gettier started with the observation that it is not easy to come by true beliefs about the external world. For example, it is not easy to go from here to there without falling over! So we need some mechanism for avoiding false beliefs, i.e., we need a way to distinguish true beliefs about the world outside our heads from false ones. Gettier proposed three conditions that any adequate theory of knowledge must fulfill. If any one of these conditions is not satisfied, then the subject does not know even though they may appear to know so. Let's see how each condition plays out in different situations. Condition 1: Knowledge Requires Awareness For someone to know something, they must actually be aware that they know it. This seems like a very natural requirement but it isn't always fulfilled. For example, let's say that you have a strong impression that your friend's car was damaged in a certain accident, yet you don't remember anything about it.