Theoretical considerations, whether explicit or implicit, guide actions and procedures applied to education-as will have been shown in the preceding chapters of this book. Writers often refer to theory, but what is really meant is not always evident. Attempts have been made to classify theories into different categories, thus by Royce (1978), who was above all concerned with psychological theory. His contribution has been aptly summarized by Rumble in an interesting scrutiny of explanation, theory and practice as related to distance education (Rumble 1992:115-16).
The term theory is problematic, indeed. In scholarly literature it is used to denote different concepts. It is frequently used to identify any systematic ordering of ideas about the phenomena of a field of inquiry (Gage 1963:102)-as sometimes when reference is made to the theory of distance education. This is evidently meant when the disciplinary areas of chairs at, for instance, German universities are described as 'theory of education' or 'theory of the school'. Theories are sometimes, in Royce's terminology, analogical. Examples already discussed in Chapter 2 (p. 19) are Fox's metaphors for four different views of learning (the transfer, shaping, travelling and growing theories). In other scholarly contexts a theory represents a structure of reasoned explanations, for which intersubjective testability is a sine qua non. As shown in the general discussion of the impact of theory on practice in Chapter 2 a theory in this sense may be expressed as a set of hypotheses logically related to one another in explaining and predicting occurrences. Empirical data can-in principle-corroborate, refute or leave unresolved hypotheses of this kind. The normal starting point in a so far unre-