In "On Ideology" Louis Althusser describes the workings of the ideological state apparatuses which use ideology as a means of "soft power" hegemonic control.
Althusser lists a few features that make up the concept of ideology:
1. Ideology has not history
This point was already presented by Marx but Althusser's formulation and reasoning is very different. While Marx held ideology to be without history on account of its decisive break from material reality, Althusser thought that ideology has a structure and function the apply in an unvarying manner and therefore ideology is a-historical for being "omni-historical". In other words, ideology presents itself as being constant an valid across history, and it therefore has no history.
2. Ideology operates individuals
Althusser held that his theory of ideology is one which demonstrates how ideology functions in a concrete manner in daily life, employing a mechanism which causes individuals to act on their own free will.
3. Ideology represents the imaginary relationship of individuals to their real conditions of existence.
Althusser is critical of the approach that hold ideology to be the imagined representation of the real material conditions of human being (the "false consciousness" tradition). He does so by simply asking why do people need such a representation of their material existence? He offers to further develop the formulation of ideology such that ideology is not a distorted image of reality but rather an imaginary distortion of people's relation to reality.
4. Ideology has a material existence
This point made by Althusser might at first seem odd, since how can something that was just defined as being "imaginary" have material existence? But Althusser's point in made clear when he argues that ideology always resides within a mechanism and its practices. For Althusser a person always acts in accordance with his world view of beliefs. This relations between action and ideology are regulated through material practices (such as going to church). For Althusser, ideology resides in a material ideological apparatus which commands ordered material practices which are regulated through ritual – practices which shape the material action of the subject which acts in conscious adherence to his beliefs.
5. Ideology hails or interpolates concrete individuals as subjects and individuals are always already-subjects
This point is made out of two theses:
1. There is no practice of any kind which is not done by means of ideology and in accordance with it
2. There is no ideology but through a subject and for subjects.
For Althusser ideology exists only through its object – the subject, and in this the subject is the constitutive category of ideology. For Althusser what characterizes ideology most is that it imposes certainties as certainties, and they make denotation meaningful, allowing for words to "point at something" in the world. One of these certainties introduced by ideology is the relation between the subject and his image as projected to him by ideology (Althusser is following Lacan here). The way ideology constitutes the subject (and itself) is through what Althusser refers to as interpolation – the appeal to the individual pre-ideological self, and in this act situating him as the object, the addressed and questioned, of ideology. Ideology gains the recognition of individuals that the space that ideology points out in the world is indeed the space that they occupy.
For Althusser, individuals are always "already subjects", even before they are born since the family, or the ideology of family, has already pre-interpolated the soon-to-born child into its subject.