A heirarchical or at least associated group of concepts based on
untestable propositions or
axioms. Such a system is, at heart, unassailable by logic or evidenciary tests. Its success depends on its utility for its maintainers.
Such systems, which may be benign or malignant, often attach to themselves ostensible demonstrations of their truth in the physical world. Observations are interpreted in such a way that they reinforce the axioms.
See: paradigm, Thomas Kuhn, Michael Polanyi