But there are other social relations necessary to maintain a society. These relations are not productive, they are reproductive. (There are also parasitic social relations, which are neither productive nor reproductive.) The modern (19th and early 20th century) academic system was not productive. Knowledge and culture are not something produced in the Marxian sense because knowledge and culture are not consumed in the sense that an ordinary television show is consumed, i.e. used up. People get tired of even classics like M*A*S*H or a magazine article about bees (so this is ordinary production), but people will never get tired of the Iliad nor the Theory of General Relativity. More importantly, reproduction needs to happen regardless of whether it can be made even temporarily profitable.
Hence I define the professional-managerial class not in terms of the tools it uses, but in terms of their social relations of reproduction.
Hence I view the class analysis of the 20th century broadly thus: during the Great Depression, the PMC as a reproductive class seizes state power in 1933. Any economic ruling class must have a countervailing reproductive class to both legitimize the authority of the ruling class and to prevent the ruling class from destroying society. Such was the role of the Church in the Middle Ages. (Both Augustine and Aquinas, for example, have much to say about secular state legitimacy.)
The capitalist class, as soon the immediate crisis has stabilized, began its project to retake state power. The capitalist class directly undermined the legitimacy of the PMC as elitist*, effeminate**, and race traitors. They co-opt the institutions (academic science and humanities, journalism, "high" culture, primary and secondary education) the PMC used to reproduce capitalist society, turning them into productive rather than reproductive institutions. They co-opted the leaders of the PMC, turning them directly into capitalists or ensuring they slavishly submitted to the capitalist class (e.g. most academic economists), abandoning the second half of their role as critics and moderators
*Never mind that the capitalist class is far more elitist than the PMC ever was or could be.
**<sarcasm> Women can't rule, n'est ce pas?, except in the exceptional case where they almost perfectly imitate men. </sarcasm>
In 1980, the capitalist class retook state power, but they were not content. Unlike the PMC, the capitalists understood that the capitalists and the PMC were enemies, and reading Machiavelli, they knew that one's enemies must be utterly destroyed. So the capitalists have continued to undermine the PMC; they will not stop until there is no such thing as a professional-managerial class as a class, only individual professionals and managers directly subordinate to individual capitalists and completely subservient to the capitalist class.
One of my main themes has been criticism of the Democratic party. I see the Democratic party not as the party of those who control information, but as the party that still tries to restore the PMC to state power. Or, more precisely, Democratic voters — aside from middle-class white women who (justly) want to preserve their access to legal abortion and minorities who (justly) fear that the Republican party will enslave or just murder them all — are those who want to return to the days when the PMC as a class held and exercised state power. I believe these voters are fundamentally mistaken. The PMC cannot regain state power; the best they can do is operate a fighting retreat, slowing the capitalists' destruction of society.
Dustin makes an important point in his comment:
My theory as a whole is that some time in the early 20th century, control over information and its dissemination actually "passed up" control over capital in being the determinant of who holds the power. Improvements in print press technology combined with the invention/improvements of radio and eventually even early forms of television in the late 1800s & early 1900s enabled for the first time in history the creation of a true mass-media and other organs of true mass-dissemination of information (and misinformation).
I think that this is what actually led to the PMC wresting of power from the capitalists in the early 20th century. The PMC were always the traditional "dealers" in media, journalism, etc., so the elite of the PMC were uniquely seated to benefit from this vast technological shift.
I agree completely that information has become the critical basis of power. However, the way that those who control information have used it fundamentally shifted only in the early 21st century, decades after the capitalists regained state power. The key is to make all information Marxian commodities, and place all of information production under capitalist commodity relations (M-C-M*), with knowledge producers as workers, not a separate reproductive class.
I really want to stress that what capitalists own (factories, money and financial flows, information) is less important than how they own it, i.e. the social relations.