ABSTRACT
Instructional design (ID) theory differs fundamentally from theories in other domains of science: Its purpose is not to explain why a part of reality is as it is but to inform us what to do when a certain instructional intent has to be realized. Thus, instructional design theory is a prescriptive instead of a descriptive theory. As any design theory it produces a kind of knowing-how instead of a kind of knowing-what. A pecularity of design theories consists in the fact that they progress not only by research but also by development. In this way, ID theory allows us to produce materials like courseware, curricula, instructional media, and so on. Another important difference between a prescriptive and a descriptive theory is that the former has to fill gaps left by the latter: Planning of instruction cannot wait until research has solved all relevant problems. That is the reason why all of the instructional design theories sketched in this section are faced with uncertainty and risk. Some of them try to deliberately overcome any uncertainty for restricted tasks of the instructional design process whereas others search to cope with uncertainty and risk by deliberately integrating it in the model.
