Excerpt from The Art of Logical Thinking: Or the Laws of Reasoning Reasoning is defined as The act, process or art of exercising the faculty of rea son; the act or faculty of employing reason in argument; argumentation, ratiocination; rea soning power; disputation, discussion, argu mentation. Stewart says: The word rea son itself is far from being precise in its mean ing. In common and popular discourse it de notes that power by which we distinguish truth from falsehood, and right from wrong, and by which we are enabled to combine means for the attainment of particular ends.