It is, however, in Plato’s constant insistence upon the principle of the division of labor, as a prerequisite for any success in the mechanical arts or elsewhere, that he reveals insight into, and interest in, productive labor. This is the basal idea in the Republic. It is also one of the chief regulations in the Laws, where its direct application to the artisan is a clear evidence that he appreciates the economic significance of the principle.155 To him, it is the foundation of all human development. Society finds its source in mutual need (ἡ ἡμετέρα χρεία). Man is not self-sufficient (αὐτάρκης). Reciprocity is necessary even in the most primitive state.156 Out of this necessary dependence arises the division of labor, a beneficent law, “since the product is larger, better, and more easily produced, whenever one man gives up all other business, and does one thing fitting to his nature, and at the opportune time.”157
The basis of this law Plato finds in the fact of the diversity of natures, which fits men for different tasks.158 In this he differs from Adam Smith, who believes that the differences of natural talents in men are much less than is generally supposed. Smith makes the propensity to barter the source of specialization, which, in turn, is based on the interdependence of men. He thus considers the diversities in human nature to be the effect rather than the cause of the division of labor.159 Plato, however, is probably nearer the truth, since the very reason for mutual interdependence is diversity of nature.160
The advantages of specialization, according to Plato,161 are four, as stated above. It enables one to accomplish more work with greater ease, more skilfully, and at the proper season. The second and fourth of these are not mentioned by Adam Smith, but he notes the resulting increase in opulence for all the people, and the development of inventive genius. He also observes that the division of labor causes the growth of capital, and that this in turn increases specialization.162 Of course Plato could not appreciate the important fact of the influence of the division of labor on the development of inventive genius, since he lived before the age of machinery.