May 31, 2018:
"Process Without a Subject" is Althusser's way of thinking how logics of complexity impel change without anyone consciously guiding them. Think of my example of Niels Bohr, complementarity, and the problematic of quantum physics. Complementarity is implied by the logic of that problematic, but, no person had thought it yet. You can reasonably understand Bohr as the result of that necessity, where someone else could and would have substituted for Bohr if he hadn't gotten to it first. Collective understanding of the problematic evolved: a concept was added to it which had previously been missing. Does it really matter which human individual had the thought?
The important implication is that history happens without a subject, whether the productive forces, "Man", or the Idea; and without a goal, whether Communism, the Second Coming, or the self-realization of the Idea. Historical change is a result of the overdetermination of the whole in its conflictual unity, like the tectonic plates of my earlier analogy, intersecting to create ruptural movement at the weakest or most stressed points of intersection. This is part of what Althusser calls "structural causality". History happens because the unity is unstable, creating a new unstable unity as its outcome. There's no forward or progressive direction implied: things might even go backward " there are counter-revolutions in history, there are civilizations which disappeared from history. There's no guarantee, no succession of grand historical epochs leading inexorably to Communism as its teleological inevitability. It's entirely possible to lose. It all depends on the balance of forces — and, perhaps ironically for Althusserians, on the decisions people make.
How does this square with Marx's insistence that "men make their own history"? A democratic formula expressing political self-determination. Althusser explains it this way: "In my opinion: men (plural), in the concrete sense, are necessarily subjects (plural) in history, because they act in history as subjects (plural). But there is no Subject (singular) of history." This means two things. Human beings in their subjectivity are formed by their social contexts, which are historical: the way they think is part of that. And, history itself isn't thinking anything.
This matters in practice because those who define the proletariat as the subject of history will as a result focus their effort on creating class consciousness. There's nothing wrong with class consciousness! The point is that exclusive focus on consciousness leaves you with a basically pedagogical model where someone — the Party, the experts, the authors of utopian systems, Georg Lukács — educates the workers until they know what's good for them. Marx's politics are antithetical to that: the liberation of the workers will be accomplished by the workers themselves. Where individuals' consciousness evolves and matures via the experience of the struggle itself. Meanwhile that pedagogical model simultaneously ignores the essentially unconscious nature of ideology, which is the real crux of things.