We might think that there is a simple and straightforward solution to the Gettier problem. Note that my reasoning was tacitly based on my belief that the clock is working properly, and that this belief is false. This seems to explain what has gone wrong in this example. Accordingly, we might revise our analysis of knowledge by insisting that to constitute knowledge, a belief must be true and justified and must be formed without relying on any false beliefs. In other words, we might say, justification, truth, and belief are all necessary for knowledge, but they are not jointly sufficient for knowledge; there is a fourth condition – namely, that no false beliefs be essentially involved in the reasoning that led to the belief – which is also necessary.