Deirdre McCloskey is right: the emergence of a new rhetoric, ideology, or set of ideas was an important factor in the rise and development of capitalism.
A big change in the common opinion about markets and innovation, I claim, caused the Industrial Revolution, and then the modern world. The change occurred during the seventeenth and eighteenth centuries in northwestern Europe. More or less suddenly the Dutch and British and then the Americans and the French began talking about the middle class, high or low — the “bourgeoisie” — as though it were dignified and free. The result was modern economic growth.
The mistake she makes is to presume that rhetoric is incompatible with materialism. In fact, ideas are just as material as anything else in shaping and transforming society.
In my view, the emergence of new subjectivities was crucial to the initial emergence, and later growth and development, of capitalism. And new, bourgeois subjectivities were (and remain) dependent on bourgeois languages and ways of looking at and talking about the world. But, and this is what McCloskey forgets, one of the conditions of existence of bourgeois rhetoric (as well as bourgeois subjectivities and much else) is a social surplus—initially appropriated and distributed from noncapitalism, later from within capitalism itself.
Both rhetoric and surplus play discreet but important roles in a materialist explanation of the rise of the bourgeoisie.
occasional links & commentary 
Well, David is right, too. I’m not surprised that he and I agree on the importance of ideas within objective circumstances, what Gramsci called a historical block. And we have been co-conspirators for decades in bringing language back into serious social science. Our only disagreement is something we can settle only by going to the facts: how much are the ideas dependent on the history of class? As the blessed Antonio put it, “the claim (presented as an essential postulate of historical materialism) that every fluctuation of politics and ideology can be presented and expounded as an immediate expression of the structure, must be contested in theory as primitive infantilism.” That’s a trifle strong, I reckon. I think it’s an empirical matter, to be settled by looking into the history of ideas and their environments. That’s volumes 3 and 4.