  Evaluating theories in physics used to be easy. Our theories provided very
distinct predictions. Experimental accuracy was so small that worrying about
epistemological problems was not necessary. That is no longer the case. The
underdeterminacy problem between string theory and the standard model for
current possible experimental energies is one example. We need modern inductive
methods for this problem, Bayesian methods or the equivalent Solomonoff
induction. To illustrate the proper way to work with induction problems I will
use the concepts of Solomoff induction to study the status of string theory.
Previous attempts have focused on the Bayesian solution. And they run into the
question of why string theory is widely accepted with no data backing it.
Logically unsupported additions to the Bayesian method were proposed. I will
show here that, by studying the problem from the point of view of the
Solomonoff induction those additions can be understood much better. They are
not ways to update probabilities. Instead, they are considerations about the
priors as well as heuristics to attempt to deal with our finite resources. For
the general problem, Solomonoff induction also makes it clear that there is no
demarcation problem. Every possible idea can be part of a proper scientific
theory. It is just the case that data makes some ideas extremely improbable.
Theories where that does not happen must not be discarded. Rejecting ideas is
just wrong.
