This is now sometimes called the four-term contingency model with setting conditions added as a fourth term.[21][22] This consists of a motivating operation (MO), discriminative stimulus (SD), response (R), and reinforcement (Srein).[23] Skinner's Verbal Behavior also introduced the autoclitic and six elementary operants: mand, tact, audience relation, echoic, textual, and intraverbal.[24] For Skinner, the proper object of study is behavior itself, analyzed without reference to hypothetical (mental) structures, but rather with reference to the functional relationships of the behavior in the environment in which it occurs. This analysis extends Ernst Mach's pragmatic inductive position in physics, and extends even further a disinclination towards hypothesis-making and testing.[25] Verbal Behavior is divided into 5 parts with 19 chapters.[1][26] The first chapter sets the stage for this work, a functional analysis of verbal behavior. Skinner presents verbal behavior as a function of controlling consequences and stimuli, not as the product of a special inherent capacity. Neither does he ask us to be satisfied with simply describing the structure, or patterns, of behavior. Skinner deals with some alternative, traditional formulations, and moves on to his own functional position.