WHEN looking over the immense literature devoted to laborproblems by philosophers, moralists, economists and sociologists, the philosophically-minded reader cannot help being struck by the fact that these writers, for the most part, abstain from defining what they intend to designate by the terms work, labor, worker, and workman. When any definition is given, there is small likelihood that it may meet the elementary requirement of embracing all the defined object and only the defined object. This current deficiency of studies on labor, although worth noting, is not particularly astonishing: everybody knows that the most familiar realities, those with which we are ceaselessly concerned in our daily life, are exceedingly difficult to express in the form of a logically satisfactory definition. In that connection, the so-called Socratic dialogues of Plato are full of profitable lessons. As soon as the persons are asked to define virtues most commonly spoken of, they become entangled in a net of contradictions, and sometimes the dialogue comes to an end without bringing forth any conclusion.