  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.
