Chap. "Psychoanalysis", pp.148-50.
In "ideology and Ideological State Apparatuses", contained in his  book Lenin and Philosophy (1971), Althusser tries to illuminate, with the implicit aid of Lacanian psychoanalytic theory, the working of ideology in society. How is it, the essay asks, that human subjects very often come to submit themselves to the dominant ideologies of their societies - ideologies which Althusser sees as vital to maintaining the power of a ruling class? By what mechanisms does this come about? Althusser has sometimes been seen as a 'structuralist' Marxist, in that for him human individuals are the product of many different social determinants, and thus have no essential unity. As far as a science of human societies goes, such individuals can be studied simply as the functions, or effects, of this or that social structure - as occupying a place in a mode of production, as a member of a specific social class, and so on. But this of course is not at all the way we actually experience ourselves. We tend to see ourselves rather as free, unified, autonomous, self-generating individuals; and unless we did so we would be incapable of playing our parts in social life. For Althusser, what allows us to experience ourselves in this way is ideology. How is this to be understood?
As far as society is concerned, I as an individual am utterly dispensable. No doubt someone has to fulfil the functions I carry out (writing, teaching, lecturing and so on), since education has a crucial role to play in the reproduction of this kind of social system, but there is no particular reason why this individual should be myself. One reason why this thought does not lead me to join a circus or take an overdose is that this is not usually the way that I experience my own identity, not the way I actually 'live out' my life. I do not feel myself to be a mere function of a social structure which could get along without me, true though this appears when I analyse the situation, but as somebody with a significant relation to society and the world at large, a relation which gives me enough sense of meaning and value to enable me to act purposefully. It is as though society were not just an impersonal structure to me, but a 'subject' which 'addresses' me personally - which recognizes me, tells me that I am valued, and so makes me by that very act of recognition into a free, autonomous subject. I come to feel, not exactly as though the world exists for me alone, but as though it is significantly 'centred' on me, and I in turn am significantly 'centred' on it. Ideology, for Althusser, is the set of beliefs and practices which does this centring. It is far more subtle, pervasive and unconscious than a set of explicit doctrines: it is the very medium in which I 'live out' my relation to society, the realm of signs and social practices which binds me to the social structure and lends me a sense of coherent purpose and identity. Ideology in this sense may include the act of going to church, of casting a vote, of letting women pass first through doors; it may encompass not only such conscious predilections  as my deep devotion to the monarchy but the way I dress and the kind of car I drive, my deeply unconscious images of others and myself.
What Althusser does, in other words, is to rethink the concept of ideology in terms of Lacan's 'imaginary". For the relation of an individual subject to society as a whole in Althusser's theory is rather like the relation of the small child to his or her mirror-image in Lacan's. In both cases, the human subject is supplied with a satisfying unified image of selfhood by identifying wit an object which reflects this image back to it in a closed, narcissistic circle. In both cases, too, this image involves a misrecognition, since it idealizes the subject's real situation. [.]
Most commentators would agree now that Althusser's essay is seriously flawed. It seems to assume, for example, that ideology is little more than an oppressive force which subjugates us, without allowing sufficient space for the realities of ideological struggle; and it involves some rather serious misinterpretations of Lacan. Nevertheless, it is one attempt to show the relevance of Lacanian theory to issues beyond the consulting room. [. H]e make us recognize that the unconscious is not some kind of setting, tumultuous, private region 'inside' us, but an effect of our relation with one another. [.; &c.] (p.150.)