Jayson Funke quoted Sweezy:
"Marx was a strong adherent of the abstract-deductive method which was such a marked characteristic of the Ricardian school... Marx believed in and practiced what modern theorists have called the method of 'successive approximations,' which consists in moving from the more abstract to the more concrete in a step-by-step fashion, removing simplifying assumptions at successive stages of the investigation so that theory may take account of and explain an ever wider range of actual phenomena."
This ignores Marx's appropriation of Hegel's ontological idea of "internal relations."
"Abstraction" in Hegel's sense means abstraction from the internal relations on which individual characteristics depend. Moving to the "concrete" means moving via direct acquaintance with these relations to the totality within which the characteristics are embedded. The "abstract-deductive method" of the Ricardian school ignores the fact of internal relations and mistakenly universalizes characteristics specific to historically limited social relations. As I've pointed out before, Marx explicitly criticizes it on this ground.
Individuals producing in Society—hence socially determined individual production—is, of course, the point of departure. The individual and isolated hunter and fisherman, with whom Smith and Ricardo begin, belongs among the unimaginative conceits of the eighteenth-century Robinsonades, [1] which in no way express merely a reaction against over-sophistication and a return to a misunderstood natural life, as cultural historians imagine. As little as Rousseau's contrat social, which brings naturally independent, autonomous subjects into relation and connection by contract, rests on such naturalism. This is the semblance, the merely aesthetic semblance, of the Robinsonades, great and small. It is, rather, the anticipation of 'civil society', in preparation since the sixteenth century and making giant strides towards maturity in the eighteenth. In this society of free competition, the individual appears detached from the natural bonds etc. which in earlier historical periods make him the accessory of a definite and limited human conglomerate. Smith and Ricardo still stand with both feet on the shoulders of the eighteenth-century prophets, in whose imaginations this eighteenth-century individual—the product on one side of the dissolution of the feudal forms of society, on the other side of the new forces of production developed since the sixteenth century—appears as an ideal, whose existence they project into the past. Not as a historic result but as history's point of departure. As the Natural Individual appropriate to their notion of human nature, not arising historically, but posited by nature. This illusion has been common to each new epoch to this day. Steuart [2] avoided this simple-mindedness because as an aristocrat and in antithesis to the eighteenth century, he had in some respects a more historical footing.
http://www.marxists.org/archive/marx/works/1857/grundrisse/ch01.htm
The idea of internal relations is also the basis of the discussion of the relation of the "abstract" to the "concrete" in the section on "The Method of Political Economy" that follows this passage.
Alfred Marshall and Keynes also assume that social relations are internal, explicitly point to the limitation this places on "the abstract-deductive method," and criticize the Ricardian school for ignoring this.
"For the sake of simplicity of argument, Ricardo and his followers often spoke as though they regarded man as a constant quantity, and they never gave themselves enough trouble to study his variations. The people whom they knew most intimately were city men; and they sometimes expressed themselves so carelessly as almost to imply that other Englishmen were very much like those whom they knew in the city. ... As the [19th] century wore on ... people were getting clearer ideas as to the nature of organic growth. They were learning that if the subject-matter of a science passes through different stages of development, the laws which apply to one stage will seldom apply without modification to others; the laws of the science must have a development corresponding to that of the things of which they treat. The influence of this new notion gradually spread to the sciences which relate to man; and showed itself in the works of Goethe, Hegel, Comte and others. ... Economics has shared in the general movement; and is getting to pay every year a greater attention to the pliability of human nature, and to the way in which the character of man affects and is affected by the prevalent methods of the production, distribution and consumption of wealth." (Marshall, Principles, Variorum ed., Vol. 1, pp. 762-764)
Ted
