Political science is methodologically diverse; political scientists approach the study of politics from a host of different ontological orientations and with a variety of different tools. Because political science is essentially a study of human behaviour, in all aspects of politics, observations in controlled environments are often challenging to reproduce or duplicate, though experimental methods are increasingly common (see experimental political science). Citing this difficulty, former American Political Science Association President Lawrence Lowell once said "We are limited by the impossibility of experiment. Politics is an observational, not an experimental science." Because of this, political scientists have historically observed political elites, institutions, and individual or group behaviour in order to identify patterns, draw generalizations, and build theories of politics.