  There are many ways we can not know. Even in systems that we created
ourselves, as, for example, systems in mathematical logic, Go\"edel and
Tarski's theorems impose limits on what we can know. As we try to speak of the
real world, things get even harder. We want to compare the results of our
mathematical theories to observations, and that means the use of inductive
methods. While we can demonstrate how an ideal probabilistic induction should
work, the requirements of such a method include a few infinities. Furthermore,
it would not be even enough to be able to compute those methods and obtain
predictions. There are cases where underdeterminacy might be unavoidable, such
as the interpretation of quantum mechanics or the current status of string
theory. Despite that, scientists still behave as if they were able to know the
truth. As it becomes clear that such behavior can cause severe cognitive
mistakes, the need to accept our limits, both our natural human limits and the
limits of the tools we have created, become apparent. This essay will discuss
how we must accept that knowledge is almost only limited to formal systems.
Moreover, even in those, there will always be undecidable propositions. We will
also see how those questions influence the evaluation of current theories in
physics.
