This thesis study is about the leading philosophers of philosophy of science of the twentieth century Karl Popper and Thomas Kuhn and their asserted views about science and scientific knowledge and the method, standard and limit of science. Popper who emphasises the deductive method of science and its standard which should be falsifiable indicates that scientific knowledge should have a testable and falsifiable pattern. Kuhn, on the other hand, discusses the standard of scientificity connected to the existing paradigm and its emerging problem solving in other words he accepts it as a "puzzle solving activity" and terminatively associates scientificity with sociological factors. Accordingly, in this thesis study by taking into consideration Popper and Kuhn's differences of opinion aimed at science and its knowledge, the arguments of development and scientific progress within the frame of their own terminology is being evaluated. Then, Popper and Kuhn's thoughts considering the standards of science and the arguments about progress and development of scientific knowledge is being transferred in a comparable and analytical manner. As a result it is advocated that Popper and Kuhn accept the existence of the change of scientific knowledge based on scientific progress and development and that this change is a change of opinion which is continuing nonstop.