  In Logik der Forschung and later works, Karl Popper proposed a set of
methodological rules for scientists. Among these were requirements that
theories evolve in the direction of increasing content, and that new theories
should only be accepted if some of their novel predictions are experimentally
confirmed. There are currently two, viable theories of cosmology: the standard
cosmological model, and a theory due to Mordehai Milgrom called MOND. Both
theories can point to successes and failures, but only MOND has repeatedly made
novel predictions that were subsequently found to be correct. Standard-model
cosmologists, by contrast, have almost always responded to new observations in
a post-hoc manner, adjusting or augmenting their theory as needed to obtain
correspondence with the facts. I argue that these methodological differences
render a comparison of the two theories in terms of their "truthlikeness" or
"verisimilitude" essentially impossible since the two groups of scientists
achieve correspondence with the facts in often very different ways, and I
suggest that a better guide to the theories' progress toward truth might be the
methodologies themselves.
