What does it mean to be an "autonomous" person? This is a riddle, in Adorno's sense.
Briefly, Adorno argues that philosophy is not like science. Philosophy does not ask "questions" with "answers" in the scientific sense of the word. Philosophy does not ask questions like, "What is the charge on an electron?" with answers like, "1.602176565(35)×10−19 coulombs." Philosophy deals in riddles — negations, contradictions — which cannot be "answered" but must be "sublated" or negated again. A riddle is a negation: "When is a door not a door?" The response sublates the riddle, negates the negation: "When it's ajar." The whole system, riddle and response, dissolves the contradiction of the riddle, and, when nontrivial, creates a new level of meaning, or at least destroys a delusion. Adorno does not, however, argue that riddles are in any sense transcendental, that they have nothing to do with science; instead, science (broadly conceived), in addition to answering questions, poses or creates riddles; without science, there would be no riddles for philosophers to untangle.
Every individual's consciousness is constructed by his or her family, society, and culture. A person who develops without any human society does not develop any consciousness at all; consciousness, personality, is not by itself something latent in infants, in the same sense that a plan for their bodily development is latent in their DNA.* We have certain propensities latent in our physical neurology: the development of language, of empathy, of reason, and perhaps some instincts (or perhaps not), but there is not an actual personality latent in an infant mind; there is at most only the propensity to develop some personality.
*Yes, I know that the environment plays a crucial role in the development of the individual phenotype. But the difference between physical development is, I claim, substantively different from mental development. There is nothing at all in mental development even vaguely similar to the phenotype's genetic "latent plan."
Saying that individual consciousness is socially constructed is not, of course, to say that the development of any individual consciousness is predictable, even if it were, at root, deterministic. Development is far too complicated to be predictable in the same sense that the positions of the planets of the Solar System are predictable. But predictability is not the issue: the issue is construction of consciousness from the "outside."
So, if consciousness is constructed, if it is ineluctably social, cultural, what does it mean to be autonomous? If my consciousness is constructed by the prohibitions and compulsions of my society, in what sense am I ever anything other than radically unfree? Given that, how can we ever distinguish between a free and an unfree society? If a slave's psychology could be constructed such that he wanted to be a slave (and why could it not?) would he still be a slave?
There is also the problem of a critique of society and culture: the critic's own consciousness, the fundamental basis of his or her critique, is a construction of society and culture: all criticism is from the "inside"; it can never be from the "outside." Or at least not radically outside; every critique is from the inside of some society and culture. A judgment that a society is good or bad is not the judgment of an individual consciousness; it is the judgment of a society of itself.
Similarly, what about an individual's self-judgment? When I feel pride or guilt, about myself, where does that judgment come from? Whose judgment is it? My own? Society's? Can any judgment of myself be anything but society's domination of the self? Even this post is American capitalist culture, which constructed the consciousness and personality of that possibly fictitious thing called "Larry," questioning itself. Why should any resolution not be simply tautological?
The problem of autonomy is, I think, the true "hard problem" of consciousness. (What passes for the "hard problem" in contemporary philosophy, i.e. how can non-conscious matter form consciousness, seems to me, after years of study, to be a scientific question with an answer, or just a pseudo-problem.)