The ontological and epistemological concepts underlying Information Systems research have evolved over time. Historically research in positivist and quantitative paradigms explain phenomena by identifying mechanical-causal factors or by logically deducing outcomes from general laws. As interpretive and qualitative approaches have become accepted, new types of explanatory knowledge have been based on interactions, processes and human intentions. Since IS artifacts are purposeful inventions intended to create new realities, the inclusion of knowledge claims derived from alternative explanations of phenomenon may provide new insights. Functional explanation provides a means of comprehending phenomena such as intentional actions, adaptive behavior, and environmental or cultural selection that are not subject to purely causalmechanical explanations. A functional orientation provides another level of explanation beyond the current focus of explanation, by examining what function(s) human behaviors and information systems play, rather than what structure and composition underlie a phenomenon. Functional explanation frames questions about how people use IS artifacts, adapt, and find multiple paths to attain functional goals. Implications for the evaluation of research outcomes and for future research are discussed.