The mutability of what constitutes professional knowledge vs. what constitutes craft is key to Plato’s adoption of various argumentative angles about labor and art in the Ion and the Republic. Plato offers "no general and systematic account of either" (Perry) but rather overlapping treatments, according to the design and the rhetorical goals of individual dialogues. The relationship of knowledge to work is complex and changeable, and so, as it develops, is the relationship of work to product. Because he does not suture the concept of product to commodity, Plato frees himself to recognize the productivity of multifarious kinds of labor, and to discuss the variety of material, epistemological, moral, and social "products" they generate, all of which are equally necessary to sustain his Republic.

	Without the commodity as the keystone to organizing and assessing work, the principle of value that Plato adopts in the Ion is the laborer's epistemological mastery (rooted in techne, episteme or both) of his labor. When Plato catalogues different professions, including professions that do not generate concrete products such as “doctor” and “charioteer,” his criterion for their legitimacy as “professions” is that they exercise specialized knowledge. Or, by contrast, the work of rhapsody is the exception that proves the rule: it ventriloquizes the professional knowledge of other labors but does not constitute valuable labor because that knowledge is borrowed – and this exception presupposes that the legitimate exercise of specialized knowledge is what makes a citizen's labor valuable. The conclusion to which Socrates leads his guest in the Ion is that rhapsody, which Socrates has determined to be epistemologically empty, is not a real profession: that Ion, who lies that he possesses “knowledge or mastery of a profession” and is “not a master of [his] subject,” is therefore “not [a] master of a profession” (23).

	In the Ion Homer is not on trial, his interpreter is. In the Republic dialogue with Glaucon the professional value of poets themselves is attacked: they are either interpreters of other craftsmen’s knowledge, or interpreters of interpreters of ideal images (making Ion, who interprets poetry, the interpreter of the interpretations of interpreted images). The basis of this argument is again in knowledge or lack of knowledge – either practical craft or knowledge-of-forms would do, but Plato finds poetry void of both. Homer spoke but could not teach, let alone do; he did not edify his countrymen or educate disciples; he was not “truly a knower of the things which he imitates,” and “if Homer had really been able to educate men and make them better, from the fact of being capable not merely of imitating but of knowing the subjects in question,” his social and professional life would have reflected his usefulness to other men.

	Where product is concerned, the value of a product is correlated in the Republic not to the raw quantity of homogeneous labor hours necessary for its production, but by the degree to which its craftsman knows his craft. This is partly a matter of education, and party a matter of affinity – inclusive of (among other elements) knowledge-of-forms and effective knowledge-in-practice. Socrates explains to Adeimantus: “We are not all alike; there are diversities of natures among us which are adapted to different occupations... and if so, we must infer that all things are produced more plentifully and easily and of a better quality when one man does one thing which is natural to him... and leaves other things” (CITE).

	The emphasis on knowledge of labor, and the complex and changeable relationship of knowledge to labor, is the quality of Plato's divison-of-labor model that most distinguishes it from a commodity-oriented model. What is the role of techne and episteme in a commodity economy? It seems possible to me that, because those professions whose practice is most tied up with episteme are the same professions that Smith considers unproductive, the emphasis on commodity must be predicated on the abstraction of knowledge  from the equation. To ensure that the system is functioning effectively, strategies for the profitable production of commodities – the “knowledge of principles” that must structure craft – should be established on an institutional level and not dependent on the knowledge of individual laborers.  In order to imagine the creation of a product without the contribution of a skilled craftsman, it is necessary to imagine a crafting process that is epistemologically empty – or whose epistemological conditions of production are so far abstracted from the actual labor process that they seem absent. For example, we can imagine an assembly line of machines that produce toys: none of these machines need to be educated in the principles that make them function (episteme) or trained to perform their work efficiently (techne). Higher in the hierarchy of production, some person must have the episteme to understand the principles on which these machines could function, and perhaps the techne to make blueprints for them. Other workers must assemble and test them. But the system works the most profitably when the least people are paid to know, and the most people are paid to do, so that wages are channeled directly into the generation of the commodity.

	Mechanized labor and assembly-line production may not be the best examples here, considering neither of them were prevalent in Smith and Ricardo's time. But Smith's pin factory is an argument for the specialization of productive labor at a level that makes even techne an afterthought. By the time Smith and Ricardo set forth their models for the division of labor,  craft/labor and knowledge/theory are separate enough concepts to sustain an argument about division of labor that never needs to address the expertise of the laborer. This model is rooted in the labor-commodity relationship rather than the laborer-labor relationship. To Plato, it is the hetereogeneity and the specificity of labor which makes it valuable. But in Smith’s pin factory labor is a “homogeneous factor”; .... “increased production, which the division of labor makes possible, is the result of the organization of work within the enterprise and essentially unrelated to the talents of the individual workmen” (“Smithian Economic Analysis”, Paul McNulty, in “Adam Smith: Critical Assessments, Volume 3”).  And this evolution in how craft is identified – away from the more inclusive and aesthetic character of techne, and towards concrete “labor” and “product” – is indicative of the widening disparity between the dialectics of aesthetics and economics.