Figure 1.

The three explanatory processes that underlie scientific explanations. Descriptive theories address the question of “what is the phenomenon?” and identify the repeatable characteristics of that phenomenon. Mechanistic theories address the question of “how does the phenomenon arise?” and explains the phenomenon in terms of the parts and interactions of other phenomena at lower levels of abstraction. Normative theories address the question of “why do the phenomena exist?” and allow a comparison of the phenomenon to an identified function or goal. Normative theories allow the determination of whether a process is achieving its goal; inadequacies generally imply an incomplete understanding of the limitations engendered by processes at a lower level of abstraction.