In order for us to understand something for example P, the standard traditional of knowledge is that P has to be true. A person cannot know a proposition that is false. Secondly a person has to belief it, you cannot know something unless you belief in it and thirdly, you have to be justified in believing it. This is the standard conditions of knowledge, justified true belief. If I vaguely believe in something without any strong belief, then that might not be enough for knowledge. For example if I am 50 percent sure that it is going to rain tonight and maybe it is justified because I saw the weather forecast yesterday. However this is not considered to be knowledge because that kind of weak belief is not enough.
To have knowledge a person should have a belief. For example it is not yet known how to cure cancer. The idea to cure cancer is not in anyone’s mind because that idea is not known to anyone, it is not knowledge. Knowing how to cure cancer requires true belief how to cure it. Knowledge has to be a true belief and not just any belief. I could belief that my computer is a table; this belief would not be knowledge. For anything to be knowledge it has to be true and correspond to the facts. For that belief to be true, my computer has to be a table and not just for me to imagine it is.
In order to know P we have to belief P. For example if I was in a pub quiz and every question is related to capital cities and I have to answer which countries belong to capital cities but I don’t know any of these. Therefore I write down the answers but all of the questions to which I have answered were all guesses but I get them all right. However there is some plausible explanation to this. It could be that when I was in school I learned all the countries and their capital cities. Even though I have completely forgotten those lessons I am able to answer the questions accurately. Therefore I had unconscious knowledge of the capital cities and so I had an unconscious belief. Therefore knowledge does require belief. You can have unconscious knowledge but only if you have unconscious belief and show some consistency.
However Gettier argues that for knowledge Justified True Belief is not jointly sufficient. He gives counter-examples where a belief was true and the person was justified in believing it but the justification did not relate to it in the right way therefore leaving it as a matter of luck that the belief was true. For example if I see a friend driving a car I may think that he owns a car and so my belief is true and justified, but on this day he was driving a friend’s car, therefore I don’t know you own a car because this is only coincidental to my evidence. Another example would be, suppose I am in the desert, I see what is in fact a mirage. I think or I am justified that I am seeing an oasis. Therefore I point and tell my friend that there is an oasis over there. However there is an oasis but it is hidden behind the sand dune. What I am seeing is a mirage but coincidentally there is an oasis in that direction. So I believe there is an oasis over there, it is true that there is an oasis over there; I am justified in believing there is an oasis. It looks like I have justified true belief but it is not the case of knowledge.
Another example in which the justified true belief is not jointly sufficient which is slightly plausible to Gettier work is, suppose there are hundreds of applicants for a single job however only two of them have made it to the final stage. One of the applicants is very qualified while the other is less of a qualified. We might consider that the well qualified man is going to get the job because of his qualifications. Therefore I believe that that the qualified man is going to get the job and I have a justified believe that the man is going to get the job. However unknown to me there is a secret talk going on, involving bribery or blackmail and therefore the least qualified man gets the job. In this situation I had a justified belief that the man was going to get the job. It is true that a man did get the job but my justification led me to believe that the well qualified man would get the job when actually the man getting the job turned out to be true by a different route. These cases show that they refute the standard justified true belief of knowledge.
Karl Popper argued that if everything has to be justified then to have a theory you have to have another theory to justify it. But that theory that justifies it also needs another justification and then that theory needs justification and so on. This is called an infinite regress. If someone belief that knowledge is justified true belief what this lends you to do is to spend your time trying to belief that beliefs are right. However Karl Popper takes the opposite view, he argues that instead of focusing what is true about belief, we should look for problems in them and try to correct those problems. For example is someone beliefs that killing is wrong, does this include self-defence or killing animals. Popper argues that we should think about these things, try to poke holes in our own theories and fix them. People who devote themselves in justification devote themselves in thinking their right. Popper sends his efforts into criticizing his beliefs to get better one. Karl Popper argues that we are trying to find the truth, he does not mean looking for the final end, we cannot be looking for truth we are sure about because we can always be mistaken and secondly trying to find the final truth is trying to find the foundation for which Popper argues cannot work. Popper argues that we should take our existing theory and see what’s wrong with them. We do this be criticizing them in order to find the problems and errors and then try to correct them. By correcting the error, the new theory would contain more truth then the old one.