Commentary What is theory?

Theory is vital in science, including evolution and ecology, yet is seldom defined. Theory is often amorph-ously described as anything abstract or mathematical, or is simply defined as the opposite of empirical work. By contrast, I explicitly define theory as the formation of testable hypotheses, while defining empirical work as hypothesis testing. This pair of definitions highlights the false dichotomy between theory and empirical work insofar as models, mathematics, and methods do not fall in either category, but instead provide the operational link between theory and empirical work. While multiple hypotheses and auxiliary assumptions may be too inter-twined to discern which one is actually falsified by a given data set, hypothesis formation and hypothesis testing are still stalwarts of science. Finally, I discuss the odd structure of theoretical papers and proposals within a tripartite parsing of science composed of theory, empirical work, and math/models/methods