While I know next to nothing about the philosophy of science, I would think about scientific models and explore whether there are features of these models that should be required in order to say they make a good theory or whether any model that predicts the data is as good as any other. From this question it would be interesting to explore the question of what it means to "understand" the world. What are the criteria of knowledge in Science? I have learned from this forum that many believe that the only way to understand the world is through models and that all of our thoughts and areas of knowledge are merely ways of modeling sets of observations. Some say that any model that describes accurately and predicts is as good as any other and that they differ not so much in whether they are right or wrong but in the domains of observation that they describe. This viewpoint also tends not care about what is really going on and in fact may deny that "what is really going on" has any meaning. I would like to explore whether this really true and ask whether there are valid criteria of knowledge that require more than modeling only. Historically,this model-only view has existed since the Ancient Greeks but there has also been another point of view. This other view rejects the idea that any model is just as good as any other and imposes as a criterion of knowledge, a principal of design or sufficient reason. While I can not exactly define this, I can illustrate it with some examples that I have read about. - In one of Plutarch's lives he addresses an empirical modeler who explains the behavior of a sundial. Paraphrasing Plutarch, his worlds were " Oh you empirical scientists! You tell me that you understand the sundial. You explain that you can predict the path of the sun's shadow as the day passes. You even tell me how the length and path of the shadow will change with the four seasons. But which one of you can tell me that it's purpose it to tell time?" I interpret this to mean that without knowing the purpose we do not have knowledge even though we may have a good empirical model. It is sort of like in a murder trial we need motive as well as weapon and opportunity. - The Ptolemaic system for the orbits of the planets was not only accurate but predicted the motions of the known solar system. Further, when after a long time it started to become noticeably off, it could be easily adjusted. The methodology, approximation by superposed circular motion, was not unlike modern Fourier analysis and could always be made arbitrarily accurate. Despite its success, the Ptolemaic system was sometimes rejected because the modeling circles had centers with nothing in them, just empty space. These "quintessences" were viewed as arbitrary and some felt that no understanding of the world could be based on the construction of arbitrary points in space. It was felt that this did not represent a rational Universe and that God would not act arbitrarily. The model, though empirically successful, was thought to be wrong. - Newton's physics did not work in every frame of reference as Newton was well aware and so he postulated an "absolute space" where his laws were true and which could be verified in any frame of reference moving uniformly with respect to it. Leibniz and others objected to his theory precisely because it required this absolute space. How was it that a rational Universe could only reveal its laws to special observers? Newton's absolute space was to Leibniz much the same as Ptolemy's quintessences. He said that Absolute space violated the principle of Sufficient Reason which I guess is what the demand for rationality became in modern times. The objection on Absolute space was finally remedied with the Theory of Relativity. I find it remarkable that the General Theory was discovered on the demand for rationality rather than in an attempt to explain yet unexplained phenomena. Einstein it seems was asking for a rational theory of gravity - one without mystical and arbitrary forces - and was not trying to expand a model to new data. In the end, the non purely empirical school of thought demands more than just a model from a scientific theory. Maybe it really requires a theory that explains the world as though there were a rational creator even if there isn't one. For without such a theory, as Plutarch argued, there can be no knowledge. - It also seems that the belief in rationality has inspired much of Physics and wonder whether knowledge can really advance without it. If we question which thought processes lead to new science perhaps we find that the demand for rationality is required. For instance, I believe the not-models-only objection to the Ptolemaic quintessences helped to inspire modern Physics. I think for Kepler and Copernicus, it was reassuring that the Sun was at the center of their models's orbits. In fact, I think it gave them confidence that their models were right. I even think that Kepler believed that God resided on the Sun and guided the planets with a force analogous to magnetism. This again told him that his model was right and seems to be the first idea of gravity. So maybe modern physics was brought forth through rejection of what was seen to be an arbitrary - though successful - modeling technique - and was inspired by a desire for a model that was consistent with rational design.