Brandom is a systematic philosopher, and he has always been clear that his aims are not principally historical. Nonetheless, like Pippin, he considers it very important to argue that Hegel, despite all his criticisms of modernity and admiration for Plato and Aristotle, regarded modernity’s advent both as the single most important event in history and as fundamentally progressive. Brandom’s uncharacteristically telegraphic argument deliberately constructs coarse historical stereotypes, with a specific, edifying purpose in mind. I am a lover of the fine grain of history, deeply concerned with subtleties and ambiguities of historiography, and critical of clichés in the history of philosophy. Coarse periodizations in cultural and intellectual matters always trouble me. So, while highly sympathetic to the edifying intent, I worry about historiographical soundness of predications on coarse periodizations.
Chapter 13 of Spirit of Trust provides the best available clarification of the conceptual content Brandom means to impute to modernity. In the more careful treatment there, the order of explanation begins from a type based simply on what Hegel would call the determinate negation of immediate Sittlichkeit — a move away from the unquestioned governance of tradition. Association of this with a particular periodization is a separate, secondary move. Also, from the point of view of the edifying intent, conceptual content is what matters, not the periodization with which it is associated. So on two separate grounds, disagreement on the periodization would not really touch the main argument, which is good. (See also Alienation, Modernity.)
Having now completed a first pass through the book, I find the less careful language of the introduction repeated in the conclusion. This could be just an editorial issue. But some of the wording again sounds like periodization could come first, and again attributes major unexplained significance to Descartes, with no earlier signpost. (He refers to a suppressed chapter on normativity in early modernity that probably would have been helpful. I’m guessing it expanded on the role he attributes to social contract theories in the published text. See also Modernity, Rousseau?)
Let me try to forgivingly recollect what is going on here. In the very big picture, stepping away from tradition is progressive compared to never doing so, and Descartes did step away from tradition. In sharp contrast to the highly technical and deeply contexted discourse of the academic philosophers of his day, Descartes became famous for simple reflections in the first person addressed to a much broader audience and presupposing no acquaintance with other philosophical texts. That is to say, he became famous as an instigator of a style of writing. A kind of individualism and a kind of democratic impulse — both interpretable as counterposed to the governance of tradition — can be read into this style, so in very broad terms that gives it a proto-Enlightenment shape that undoubtedly inspired others. The large social/historical impact of his proto-Enlightenment writing style cannot be denied, regardless of the verdict we reach on the relative merits of his philosophical claims and arguments. He also tried to build a complete foundationalist system of his own, which for better or worse could be read as another expression of burgeoning individualism. In conjunction with this, he promoted a kind of know-nothing attitude toward previous philosophy, which if we are being very charitable could again be loosely tied to a sort of democratic impulse.
That said, while reflections in the first person are important in our social relations, to claim to derive the only true system of the world from first-person reflections is a terrible and extremely arrogant way to do philosophy. To think otherwise is a particularly bald example of the illusion of Mastery. The wholesale rejection of previous philosophy is another artifact of hopeless Mastery. The specific conceptual content Descartes gives us does little to improve the situation. (I’ve commented before on Descartes and representation — see the Repraesentatio post.)
The thrust of the famous cogito ergo sum was already anticipated in Augustine’s Confessions. A more detailed version was developed by Avicenna, in an argument known to the medievals as the “flying man”. He proposed a thought experiment, considering someone in counterfactual absolute sensory deprivation from birth, with the intent of asking whether awareness could be completely independent of sensibility. He argued that the person in absolute sensory deprivation would still be aware of her own existence, due to a pure immediate reflexive awareness intrinsic to the soul and independent of the body. This kind of claim would have been accepted by Plotinus, but rejected by Aristotle or Hegel. Medieval Augustinians, however, enthusiastically adopted many of Avicenna’s ideas.
More originally but even less auspiciously, Descartes argued for the incorrigibility of raw appearance qua appearance as an epistemic foundation. In Brandom’s Fregean terms, this gives us bare reference to an unspecified something, but no sense we could begin to work with. This kind of incorrigibility is a trivial truth, but because it is trivial, nothing of interest follows from it. As Brandom says, a contraction to appearance-talk is a refusal of actual commitment to anything. And we don’t want an incorrigible foundation anyway. What does any of this add to our expressive genealogy? It still seems like a node deserving of omission in a short account.
Brandom himself in his study guide to Sellars’ “Empiricism and the Philosophy of Mind” says “the Cartesian way of talking about the mind is the result of confusion about the distinction between epistemic and non-epistemic items, and the roles they can play in various sorts of explanation”. (See also Enlightenment.)