  Epistemology is the branch of philosophy that deals with gaining knowledge.
It is closely related to ontology. The branch that deals with questions like
"What is real?" and "What do we know?" as it provides these components. When
using modeling and simulation, we usually imply that we are doing so to either
apply knowledge, in particular when we are using them for training and
teaching, or that we want to gain new knowledge, for example when doing
analysis or conducting virtual experiments. This paper looks at the history of
science to give a context to better cope with the question, how we can gain
knowledge from simulation. It addresses aspects of computability and the
general underlying mathematics, and applies the findings to validation and
verification and development of federations. As simulations are understood as
computable executable hypotheses, validation can be understood as hypothesis
testing and theory building. The mathematical framework allows furthermore
addressing some challenges when developing federations and the potential
introduction of contradictions when composing different theories, as they are
represented by the federated simulation systems.
