 Several issues were involved in the view of science as a taxonomy or grammar.  The influential French positivist, Auguste Comte, along with scientific positivists like Mach, distrusted theoretical concepts in science because they saw that these concepts rely on elements of practical  experience.[6]  A prime example was the relation of the concept of gravity to the experience of weight on the surface of the earth. Comte said that gravitation is a “general fact” which is itself “a mere extension of [a fact] which is perfectly familiar to us, and which we therefore say that we know; — the weight of bodies on the surface of the earth” (Comte 28–29). Positivists believed we cannot avoid the anthropomorphic origin of theoretical concepts. It had, however, become clear to positivists who were actually engaged in the practice of science that the structure of a science is what sustains prediction, not the meaning of the theoretical terms of the science. A system of principles constitutes a logical form of explanation, and the ability of the system of principles to link disparate phenomena, more than concepts, is the truth in science. As a result, descriptions of the logical character of a science come to the fore in discussions of theory.