The purpose of scientific inquiry is first to understand a phenomenon, then to explain and to predict, and, if possible, to control the occurrence of a phenomenon. Ideally, theory integrates, organizes, and classifies the many facts documented in individual empirical studies. Theories are developed by combining logic with the results of observations. Theories may be expressed in such a way that constructs can be symbolized and the rules of logic applied to permit deductions. In other instances, a theory contains a model that depicts the relationships among constructs and permits conjecture.
Theory is what gives direction to an empirical investigation.
The process of theory development involves a continual refinement of the interaction between constructs and empirical observations in a manner that makes possible deduction leading to explanation and prediction. The input for theory development results from the research activities of observation, study, and experimentation. Theories play several roles in the development of science. However, explanation in most areas is never complete and is subject to revision as more empirical evidence becomes available. Although theory is not an absolute truth, some theories are sufficiently developed to allow prediction with a high level of accuracy.