In 1938, Adorno rejoined the Institute, which was now located in New York, and worked on the Princeton Radio Research Project, headed by Paul Larzarsfeld. While in America he worked on a number of different projects, including one with Thomas Mann on Doktor Faustus. With Max Horkheimer, Adorno sounded a pessimistic note about Enlightenment reason in the Dialectic of Enlightenment which was first published in 1947. In 1953, at the age of 50, Adorno left the United States and returned to Frankfurt to take up a position with the Institute, and in 1959 he became its director following the retirement of Horkheimer. By the end of the following decade Adorno became embroiled in a conflict with the students who occupied the Institute's offices. Adorno died in 1969 in Switzerland while writing what many believe to be his most important work, Aesthetic Theory.

Current debate on Adorno's work has, in part, centred on the extent to which he anticipates aspects of postmodern and post-structuralist thought. Particular attention is often given here to Adorno's critique of 'identity-thinking' in his Negative Dialectics . While it is necessary to understand what Adorno means here, we should also bear in mind a number of points which clearly separate his project from those inspired by nominally French thought.

Let us begin with science. While Julia Kristeva has said that structuralist-inspired semiotics must take its cue from developments in quantum physics, and while Jacques Derrida cites Gödel directly in formulating his philosophical notion of ëundecidabilityí that is, while semiotics and post-structuralism in France have forged bonds between the natural and the human sciences - Adorno, like other members of the Frankfurt School, saw modern science as inherently positivist. As Adorno aimed to produce a dialectical thought which did not 'positivise' in any way, science in general was treated with the greatest suspicion, if not contempt. Science in Adorno's philosophy would even be the form of thought he most opposed given that, like positivism in general, it is seen to be absolutely dependent on the logic of identity. Philosophy has allowed itself to be terrorised by science, Adorno claims. But philosophical truth does not equal scientific truth, and philosophy should not shy away from this. In sum, 'Philosophy is neither a science nor the "cogitative poetry" to which positivists would degrade it in a stupid oxymoron'.

Second, Adorno retains - albeit more in his works of cultural criticism than his philosophy - the distinction between 'essence' and 'appearance' (a distinction rejected by contemporary French thought of post-structuralist inspiration) in order roundly to reject the superficial nature of appearance in modern capitalist society. For Adorno, the world of appearance, as for Plato before him, is a world of images and mere semblances, a world of relativism and, most of all, of reification. On this reading, reification and commodities in the capitalist world are almost identical; commodities take on a life of their own independently of the conditions of their production. Commodities hide the truth of their illusory nature. They serve to titillate 'the reified consciousness' which is 'a moment in the totality of the reified world'. Moreover, by contrast with recent French thought, ideology still plays an important part in Adorno's analyses of social conditions, even if, as he shows in Prisms, the analysis of ideology can no longer rely on the 'transcendent' method, where the critic claims to be detached from the milieu being analysed. The difference between 'essence' and 'appearance' entails the ideological effect of reification. For behind the reified appearances, lies the truth of the 'phantasmagoria' of commodity production. This truth is that human beings, despite what they might think, are unfree; they have restrictive forms of thought and action imposed upon them by the existing social conditions of capitalist production; they live in 'the open air prison which the world is becoming'.' People adapt to these conditions rather than oppose them. Consequently, the freedom that Simmel talks about in the same context is a myth. 'In a state of unfreedom', says Adorno, 'no one, of course, has a liberated consciousness.í

Finally, Adorno places far more weight on the role of consciousness than is the case with comparable French thinkers such as Lacan or Foucault. Although he spent time developing ways of escaping a reductive view of the individual as 'socialised', and although his position here is in other respects complex, Adorno's view of the unconscious is extremely simple. First of all, the unconscious (like Freud's work in general) receives little elaboration in Adorno's philosophy. On one of the rare occasions in which he actually refers explicitly to the unconscious in Negative Dialectics, he says:

'When the doctrine of the unconscious reduces the individual to a small number of recurring constants and conflicts it does reveal a misanthropic disinterest in the concretely unfolded ego; and yet it reminds the ego of the shakiness of its definitions compared with those of the id, and thus of its tenuous and ephemeral nature'.

Even if 'shakiness', 'tenuous', and 'ephemeral' suggest a movement away from the primacy of consciousness, there is little evidence that the unconscious poses a real obstacle to philosophy or to thought.

In other words, Adorno still seems to be far more beholden to a logic of identity than some of his more recent readers suggest. On the other hand, it is also true that his aspirations are in the direction of a thought that is not wholly and solely indebted to the logic of identity. Thus when he begins to rethink the nature of philosophy in Negative Dialectics, Adorno makes two key points: first, that philosophy 'lives on' after the Marxist attempt to discredit it for being too idealist had failed; and, second, that philosophy needs a sense of its own impotence before the materiality of the world in order that it might remain creative and open to the new. The materiality of the world is philosophy's inexpressible side. The essential character of philosophy thus consists in being only too well aware of the limitedness of the concepts with which it works. 'Disenchantment of the concept is the antidote of philosophy.' In effect, a truly creative philosophy - which, for Adorno is philosophy - seeks out those things which are a challenge to thought itself. These things can be generally designated by the terms 'heterogeneity', or more pointedly, by 'nonidentity'.

Unlike Hegel's system in which the heterogeneous element would be reclaimed dialectically through the principle of the ,negation of the negation', Adorno announces the principle of 'negative dialectics', a principle which refuses any kind of affirmation, or positivity, a principle of thorough-going negativity. Thus negative dialectics is nonidentity. This key element in Adorno's thought has a number of synonyms in addition to the ones we have given above - for instance: 'contradiction', 'dissonance', 'freedom', 'the divergent', and 'the inexpressible'. Despite the importance of nonidentity, Adorno also says that no thought can in fact express nonidentity: for 'to think is to identify'. Identity thinking can only think contradiction as pure, that is, as another identity. Where, and how, then, does nonidentity thinking actually leave its mark on thought? In short, what is the material basis of negative dialectics in thought?

To begin with, the material aspect is not philosophy as poetry, or as art. For philosophy as art is equivalent of the erasure of philosophy. Nor is philosophy permitted, according to Adorno, to give in to an aesthetic impulse. This does not of course preclude experimenting in the presentation of new concepts, a process which may lead to poetry, just as the most avant-garde art might be an immanent conceptualisation. Nevertheless, philosophy must 'void its aestheticism'. 'Its affinity to art does not entitle it to borrow from art,' and here Adorno continues the point in a tone for which he has become notorious '. . . least of all by virtue of the intuitions which barbarians take for the prerogatives of art.' All that philosophy can do in such circumstances is continue as philosophy. To give up in light of the impossibility of expressing nonidentity would imply that philosophy had misunderstood the heterogeneous, dissonant nature of nonidentity; in other words, to give up in this sense is to misunderstand that nonidentity is impure - not even a pure contradiction. 'Thoughts intended to think the inexpressible by abandoning thought falsify the inexpressible.' Nonidentity is possibly philosophy's hidden, negative telos. It was thus Marx's mistake to think of the end of philosophy in precisely these terms.

The other sense in which philosophy might come to an end is if it took the form (as in Hegel) of Absolute knowledge. Then every problem confronting philosophy - especially its relationship with the material world would be resolved through the affirmative principle of the negation of the negation which produces an affirmation.

By a surprising series of reversals, Adorno turns philosophy's potential limitations into a philosophical gesture whose implications are perhaps now only beginning to be appreciated. 'In principle', Adorno confirms, 'philosophy can always go astray, which is the sole reason why it can go forward'. Philosophy, therefore, is a negative dialectics in the strongest sense; it is itself the very nonidentity it seeks to conceptualise. In this, the role of language becomes crucial because language is equivalent to the presentation of philosophy's 'unfreedom' as equivalent to the impossibility of conceptualising nonidentity. Were language to cease to be important in philosophy, the latter would 'resemble science'.

Adorno's declarative statements in Negative Dialectics need to be read in conjunction with his work in aesthetics and literary criticism. In this regard, Minima Moralia: Reflections on a Damaged Life, written during the Second World War in an aphoristic style counters, like Kierkegaard (on whom Adorno also wrote), Hegel's dialectical theory which 'abhorring anything isolated, cannot admit aphorisms as such'. In his reflections on a diversity of topics, Adorno seeks - practically, we may assume - to make a philosophical statement, one that takes up the place of the heterogeneity of human experience.

Similarly, Adorno's attraction to avant-garde music and art, particularly the music of Schönberg, Webern, and Berg, was strongly motivated by a desire to see avant-garde works defy the homogenising effects of the commercialisation (read: reification) of art, where art objects would be reduced to exchange-value. Subjectivity is reduced to the status of a 'mere object' by exchange-value. There is thus a desire in Adorno to preserve the sanctity, as it were, of subjectivity embodied in the art object, against the onslaught of the market where value is equated with price. Through a paratactic style (juxtaposition of statement with the link between them being made explicit), and other devices, Adorno's presentation of his theory of aesthetics in Aesthetic Theory participates in an effort to by-pass the reduction of art and thought to the culture industry. Unlike his French counterparts who tend to engage with exchange-value in order to subvert it from the inside, Adorno lauds difficult art and philosophy; for, as he sees it, only through a struggle to understand can value be given its true rights here. Modernism, as the movement embodying the renewal of value, would thus be essentially avant-garde where the work of art -'even the simplest'- becomes a complex tour deforce. This avant-garde strategy is the point of resistance to reappropriation by the market system.

Some (e.g., Lyotard) have come to see Adorno's approach as a last-ditch attempt to maintain a boundary between high art and popular culture just at a time when the logic and social basis of such a boundary is becoming untenable in the name of the very political values (e.g., opposition to conventional Marxism) to which Adorno himself subscribed. Furthermore, in light of Bataille's work, it is clear that exchange-value can be subverted as much by the very 'low' elements (obscenity) in social life, as by the highest and most spiritually charged products of the avant-garde. Both can entail the distancing necessary to counter the ephemeral immediacy of consumer pleasure. Perhaps the 'low' even more than the 'high'; for ultimately 'high' art depends on the judgement of criticism as to its nature and quality; it is thereby incorporated into the play of concepts. In other words, avant-garde art and philosophy become interdependent and all the more so - if an analogy with Negative Dialectics holds - to the extent that the art object becomes inseparable from its materiality (nonidentity). Grasping the force and significance of avant-garde art requires the use of concepts which can never do a work justice; for the materiality of the work constitutes its uniqueness, and this defies conceptualisation. As Peter Osborne has remarked, 'It is out of this critique of identity-thinking that Adorno's basic conception of aesthetic experience, as the experience of the "non-identical", arises.'

Overall, Adorno's Aesthetic Theory struggles to reach an accommodation between avant-garde art that risks being 'normalised' and reified in capitalist society, and the essentially radical autonomy of art objects which qua art objects are singularly out of harmony with the social conditions (including criticism) which enable them to speak at all. There is another aspect to the question, however, one that perhaps Adorno forgets. It is that the conceptualising facility itself could become impoverished through a continual rejection of its worth and efficacity. While the detail of art which defies the system because it defies conceptualisation is no doubt fundamental, conceptualisation might well be also. In other words, what Adorno does not readily acknowledge is that a certain degree of identity philosophy is as essential as material nonidentity.