The Idea

Back when I was in college, I underlined and put a star next to this passage from Marx's "German Ideology":

For each new class which puts itself in the place of one ruling before it, is compelled, merely in order to carry through its aim, to represent its interest as the common interest of all the members of society, that is expressed in ideal form: it has to give its ideas the form of universality, and represent them as the only rational, universally valid ones. ...

Every new class, therefore, achieves its hegemony only on a broader basis than that of the class ruling previously, whereas the opposition of the non-ruling class against the new ruling class later develops all the more sharply and profoundly. ...

Once the ruling ideas have been separated from the ruling individuals and, above all, from the relationships which result from a given stage of the mode of production, and in this way the conclusion has been reached that history is always under the sway of ideas, it is very easy to abstract from these various ideas "the idea," the notion, etc., as the dominant force in history, and thus to understand all these separate ideas and concepts as "forms of self-determination" on the part of the concept developing in history.