This article by Paul F. Lazarsfeld critically examines the logic and application of typological procedures in empirical social research, drawing on the foundational analysis by Carl G. Hempel and P. Oppenheim. Lazarsfeld introduces the concepts of attribute space and reduction and distinguishes between three types of reduction: functional, arbitrary numerical, and pragmatic. He elaborates on the process of “substruction,” whereby a system of types is logically traced back to an attribute space and reduction, enhancing the rigor and utility of typological schemes. Through practical examples—from assessing social advantages based on demographic attributes to analyzing family authority using multidimensional reductions—Lazarsfeld demonstrates how substruction clarifies omissions and overlaps, facilitates empirical classification, and enables further theoretical refinement. The article emphasizes that typological classifications in social research are most robust when grounded in systematic analysis of their underlying logic, advocating for the deliberate use of reduction, substruction, and transformation to link types with attribute spaces for improved empirical application and interpretability.