The central thesis of this article is that measurement units are theoretical concepts because measurement presumes theoretical definition. New theoretical constructs can be defined in terms of algebraic combinations of previously defined measurement units. Physics has developed an impressive hierarchical knowledge structure on this basis. The unitless measures favored by psychology preclude the generation of such a knowledge hierarchy. It also leads to definitions of reliability and validity in correlational terms which can result in inaccurate measurement. Psychology has long used (...) time as a fundamental unit. Adoption of a second measurement unit would enable construction of a psychological knowledge hierarchy to begin. (shrink)

The major premise of this paper is a well accepted definition taken from the mathematics of information theory; information exists only when uncertainty is reduced by some amount. The minor premise of this paper is that all valid explanations be informative to some degree. Hence, the thesis of this paper is that all valid explanations must reduce uncertainty. The quantification of information is explained, direct and indirect explanations examined, equivalence with regression, correlation, and analysis of variance described, weak and strong (...) versions of uncertainty reduction presented, relationships with determinism and development mentioned, qualitative explanation accepted, and invalid examples of redescription as explanation illustrating reductionism, traits, and cognition are provided. 2012 APA, all rights reserved). (shrink)