A curious factoid.  The frequency with which the term 'alienation' is used in the English language has fluctuated considerably, but from about the beginning of Marx's oeuvre to the mid-point of the twentieth century, it actually declined in useage (from about 5 uses per million words to 2 uses per million).  After the 1950s, however, its use suddenly and dramatically increased to almost 12 per million.  

The occasion for this, of course, must be the 'recovery' of Marx's earlier works, such as the Economic and Philosophical Manuscripts (pub. 1927), The German Ideology (1932), and even the later manuscripts of the Grundrisse (1939).  All of these seminal texts became the basis for a New Left critique of Stalinism after the Twentieth Congress of the CPSU and the suppression of the Hungarian workers' uprising, predicated on 'socialist humanism'.  And amid the ensuing intellectual glasnost, humanistic concerns with consciousness and alienation became hugely influential on the Left and in the academia.  That tide may have receded somewhat, but the concept has now been firmly established, surviving the anti-marxist reaction in the academia.

So, then, what is the concept?  What are its objects and what relation between those objects does it show?  I let slip in a previous post that I had my doubts about the concept  of 'alienation', especially if it was based on the concept of 'human nature'.  Someone asked me, though - so what is your conception of alienation then?  Do I need one?, I retorted.  No, but there isn't just one notion of alienation in Marx.  That is, to reject the problematic of the theoretical human being (species-being) is not necessarily to reject all uses of alienation in Marx.  Indeed, it is a truism about Marx's works that for all his extraordinary rigour he often used concepts in quite different and inconsistent ways, some highly speculative and others more concrete, leaving readers to sort out the diverse usages.

As far as I can make out, two major concepts of alienation emerge in Marx's works.  First, in the early work, there is the separation of humanity from its species-being, from its essence as a labouring being.  This is Marx at his most essentialist.  Humanity is alienated, ie divided in itself; workers are separated from their own nature, but also from the nature of the other workers.  Second, in the later work, there is the alienation of humanity's collective labour and its products in the capitalist mode of production, and their reappearance as a set of reified, objective forces.  This is a historically specific conception of alienation, and relies on no general philosophy of human nature.  One way of coping with this inconsistent useage is to assert that there is no contradiction between the two; the former implies the latter.  This may be true in a sense, though it is by no means clear that the latter conception, emerging from a critique of the political economy of capitalism, implies the former, emerging from a critique of speculative philosophy.

Althusser rejected the notion of alienation strictly in its former sense, because he rejected a philosophy of history grounded in a human subject undergoing self-realisation.  He was in this sense a theoretical anti-humanist.  This did not entail a blanket refutation of ideological humanisms, certainly not those which animated workers rebellions against the Stalinist machinery, for example.  It was not a refutation of the centrality of human liberation to the communist project.  It was not a denial of human agency.  It simply stated that the concept of 'humanity', or 'man' in the old sexist idiom, played no theoretical role in historical materialism.  That is, that any references to 'humanity' in the context of marxist theoretical analysis are either rhetorically external to its object, and thus could be dispensed with without altering the theoretical product, or result in a distortion of marxist theory. 

The démarche of marxism, the 'epistemological break', was to found a science of history, historical materialism, on something other than a philosophy of human essence, species-being and so on: classes and class struggle, modes of production, forces and relations of production, capital as a social relation, infrastructure and superstructure, are the theoretical objects of historical materialism.  To understand the mode of production and its various relations, one need have no resource to the human being as a theoretical object: social relations occur not between human beings (qua some general species essence) but between agents (capitalists, workers, etc., all endowed with quite distinct capacities, interests etc).  Certainly, 'men' make history, but not as its subjects in the old philosophical sense (I know, this covers a multitude of sins).  Rather, they make history "under circumstances directly encountered, given and transmitted from the past", that is as historically constituted agents, bearers of a structure.  In this sense, theoretical humanism and its concern with alienation is seen as a pre-marxist position.

One strategy of opposing this argument is to insist on the resistant realities of human flesh, its capacities and needs - to eat, drink, orgasm, etc.  Surely, the whole business of modes of production, social formations, classes, infrastructures and superstructures, presupposes a human essence?  But unimaginative retorts of this kind really miss the point.  There is no 'unalienated' way to eat, drink or orgasm in the sense that social relations necessarily 'intervene', shape, regiment, serialize and organise these activities in a particular way.  It is on the basis of social relations and the technologies of power that are developed to facilitate their reproduction that such needs, drives and capacities are convoked into the form of subjectivity.  We are most of us capable of sustaining an orgasm, but there is no essential orgasm that is ontologically prior to sexual subject-formation.

If one must have a conception of alienation, and if this concept must explain something about subjectivity, then I think we're back to attempts to fuse Marxism and psychoanalysis (or rather to conscript psychoanlysis into Marxism as a regional theory governed by the general theory of historical materialism).  Because, of course, the fundamental insight of psychoanalysis is that human subjects are constitutively divided.  The unconscious 'speaks' through a subject that experiences it as an utterly alien presence.  Its thoughts are disruptive, subversive and totally at odds with the self-image and ideals of the subject.  So there is no myth of human wholeness for psychoanalysis.  Indeed, the whole point for psychoanalysis is that subjectivity comes into being after a fundamental 'loss' or negation.  For the normal/neurotic subject, it is the loss of jouissance - eg, the baby is weaned from its mother's breast and subject to symbolic law instated by the father - it thus becomes a subject on the basis of a 'loss' or 'castration'.  But this 'loss' is imaginary in the sense that the child 'loses' an imaginary relationship with the mother, as an extension of the mother's body - only becoming a differentiated subject after the violent inscription of the symbolic order says 'you are different from your mother' etc.  So subjectivity in psychoanalysis emerges on the basis of the loss of what one never had.

In a homologous way, you might say that the working class only comes into existence on the basis of a fundamental experience of 'estrangement', being separated from the means of production.  Yet, of course, the working class never had control of the means of production. That is what disinguishes it as a class from, say, the peasantry.  So, this 'loss' is exactly what is constitutive of working class subjectivity - the loss of what it never had.  And in a manner of speaking which is not completely parodic, you could say that this constitutive separation becomes the central alienation around which other alienations (from control over one's labour power, from the products of one's labour power, from other workers, etc) are articulated.  It is less important how far one pushes this homology than the approach it is supposed to illustrate.  It is just a way of tackling the problem of alienation in a historically delimited way, in a way that comprehends both its structural-relational and subjective effects, without collapsing into speculative idealism (humanity, separated from its essence), or vulgar psychologism (oh, look at me, oh I'm ever so fractured and incomplete and alienated from my fellow human beings, oh help, help, help*). 

*This is why I blog, you know.  I'll never be taken seriously in the academia.