This article defines and discusses the possible forms that a substantive theory relating a dependent variable in a continuous manner to an independent variable can take. The restrictions are that the variable be continuous and a ratio, an interval, or a logarithmic interval scale, admissable transformations of the independent variable may not result in inadmissable transformations of the dependent variable, and the form of the function relating the variables should not be altered by admissable transformations. The possible laws relating combinations of scale types are listed. Laws other than these are possible if the variables are discrete or related by a discontinuous function. If "the independent variable is a ratio scale that is rendered dimensionless by multiplying it by a constant having units reciprocal to those of the independent variable, then either the principle has no content or it is violated, depending upon how one wishes to look at the matter." (18 ref.) From Psyc Abstracts 36:01:1BB81L. (PsycINFO Database Record (c) 2016 APA, all rights reserved)