Theory
A theory consists of intersubjective signs of universals about essential properties and their relations, yet to be warranted by disciplined inquiry.
Note: When warranted by disciplined inquiry, a theory becomes theoretical knowledge (quantitative structures); hence it is intersubjective signs of instantial, relational, and criterial knowing that about objects which are universals.
Thompson (2006) argues that theory should predict that which we do not already know or expect:
If there are no counterintuitive results derived from a theory, and if there are no predictions from the theory that are not obvious, and if the theory does not provide outcomes that were not seen, and if the theory does not obtain results that are otherwise difficult to obtain, then there is no need for the theory.... Therefore, the purpose of a theory is to provide the means to develop mathematical, analytical, or descriptive models that predict counterintuitive, nonobvious, unseen, or difficult-to-obtain outcomes. (ATIS: Methology of Theory Construction, p. 16)
This also is helpful in distinguishing knowledge from theory. Since knowledge is a record of knowing, theory must include signs that represent relationships about what we do not already know. Therefore, a theory needs verification before it becomes knowledge. Steiner (1988, pp. 59-89) discusses criteria for evaluating theory.
For an example of application of education theory that makes unexpected predictions about education systems, based on axiomatic theory, see: