Has Science Established that the Cosmos is Physically Comprehensible?

Abstract: Most scientists would hold that science has not established that the cosmos is physically comprehensible - i.e. such that there is some as-yet undiscovered true physical theory of everything that is unified. This is an empirically untestable thesis and thus lies beyond the scope of science. However, this argument presupposes a conception of science which holds that in science theories are accepted solely on the basis of evidence. But this conception of science is untenable. Any fundamental physical theory, in order to be accepted as a part of theoretical scientific knowledge, must be (1) sufficiently empirically successful, and (2) sufficiently unified. Given any accepted theory of physics, endlessly many empirically more successful disunified rivals can always be concocted - disunified because they assert that different dynamical laws govern the diverse phenomena to which the theory applies. These disunified rivals are not considered for a moment in physics, despite their greater empirical success. This persistent rejection of empirically more successful but disunified rival theories means, I argue, that a big, highly problematic, implicit assumption is made by science about the cosmos, to the effect, at least, that the cosmos is such that all seriously disunified theories are false. Once this point is recognized, it becomes clear, I argue, that we need a new conception of science which holds that science makes a hierarchy of assumptions about the cosmos, these assumptions becoming less and less substantial as one goes up the hierarchy. One of these assumptions is that the cosmos is physically comprehensible. Hence the conclusion: improve our ideas about the nature of science and it becomes apparent that science has established that the cosmos is physically comprehensible.