This book investigates the criteria Thomas Aquinas employs to determine the moral species of human actions. Joseph Pilsner, an academic scholar, analyzes the apparent inconsistencies in Aquinas's terminology regarding moral specification. By examining the five distinct terms—end, object, matter, circumstance, and motive—Pilsner constructs a framework to determine if a unified, consistent theory of moral action exists within the Thomistic corpus.

Scholars and students of medieval philosophy frequently cite this work as a necessary resource for navigating the complexities of Thomistic moral theology. Experts highlight the text's academic density and its success in reconciling seemingly disparate elements of Aquinas's ethical system.