MAIN POINTS

A concept is an abstraction representing an object, a property of an object, or a certain phenomenon. Concepts serve a number of important functions in social science research: 1) they are the foundation of communication; 2) they introduce a point of view-a way of looking at empirical phenomena; 3) they are means for classification and generalization; and 4) they serve as components of theories and thus of explanations and predictions.

Clarity and precision in the usage of concepts are achieved by definitions. Two types of definitions are important in social science research: conceptual definitions and operational definitions. Conceptual definitions consist of primitive and derived terms. Primitive terms are those on which there is a consensus over their meaning; usually their meaning is conveyed by indicating examples. Derived terms are those that can be defined by the use of primitive terms. Operational definitions refer to sets of procedures that describe the activities one should perform in order to establish empirically the existence or degree of existence of a phenomenon described by a concept. Concepts have both conceptual and operational components; the problem faced by the social scientist involves the integration of these two levels.

Two important issues arise with the transition from the conceptual level to the empirical observational level. The first is the degree of congruence between conceptual and operational definitions. The second issue involved arises when concepts cannot be operationally defined; that is, they cannot be either directly or indirectly observed. Scientific concepts should not be evaluated only in terms of their observability but also in terms of their theoretical import; that is, some concepts gain meaning only in the context of the theory in which they are introduced.

There is no one simple definition of theory that would be agreed upon by all social scientists, and this is so because there are many different kinds of theories serving different purposes. Frankfort-Nachmias and Nachmias's classification is based on the Parsons and Shils distinction among four levels of theory: ad-hoc classificatory systems, taxonomies, conceptual frameworks, and theoretical systems.

Ad-hoc classificatory systems consist of arbitrary categories constructed in order to organize and summarize empirical observations. Taxonomies are systems of categories constructed to fit the empirical observations so that relationships among categories can be described. Conceptual frameworks consist of descriptive categories being systematically placed within a broad structure of explicit as well as assumed propositions. Theoretical systems combine taxonomies and conceptual frameworks, but now descriptions, explanations, and predictions are related in a systematic manner. A theoretical system consists of a set of descriptive concepts, operative concepts (variables), and a set of propositions that form a deductive system.

Axiomatic theory is a type of theoretical system consisting of: 1) a set of concepts and definitions; 2) a set of existence statements that describe the situations in which the theory can be applied; 3) a set of relational statements comprising axioms and theorems; and 4) a logical system for deduction.

A model can be viewed as a likeness of something; it is an abstraction or representation of reality. Models delineate certain aspects of the real world as being relevant to the problem under investigation, they make explicit the significant relationships among the aspects, and they make it possible to formulate empirically testable propositions regarding the nature of these relationships. Models are tools for explanation and prediction.

The social sciences rest on two major components: theory and empirical research. There is a controversy about which of these components should come first. According to one school of thought, developed by Karl Popper, theory should come first, followed by research. Robert Merton and others have argued for a research then-theory argument, with empirical research suggesting new problems for theory, calling for new theoretical formulations, leading to the refinement of existing theories, and serving the function of verification.