The perspectives presented above provide justification for distinguishing five different interrelated types of theory that are relevant to information systems research (see Figure 1.1, “Interrelationships among theory types.”). Each type is described more fully in Gregor, (2002).
Descriptive theory says ‘what is’ and is the basis for all other types of theory. Description and specification of constructs in theories of this type are needed (Dubin, 1978), as are descriptive frameworks that specify and classify the phenomena of interest in a theoretical domain (Cushing, 1990).
This type of theory says how and why something occurred. Theory from interpretive approaches can be used as sensitising devices that allow greater insights into familiar situations (Klein and Myers, 1999). Conjectures can be drawn on the basis of a number of limited observations that are used as a basis for hypothesis formation and theory building.
Predictive theories say what will be, given the presence of certain conditions. These theories give predictive power without necessarily having explanatory power (Dubin, 1978). Again, knowledge of this type, such as statistical regularities, can yield hypotheses for theory building.
This type of theory says what is, how, why, and what will be. It is the type of theory commonly specified in the ‘scientific’ perspective (Dubin, 1978).
Design theory is the prescriptive type of theory that gives principles for the construction of a tool or artefact to meet a set of meta-requirements (Hevner et al., 2004; Iivari, 2003; Simon, 1996). Design theory is informed by, and can inform, theory for explaining and predicting.