  A more critical understanding of law’s relation to ideology, and the role and purposes that ideology serves, is found in the writings of Karl Marx and Friedrich Engels. Like De Tracy, Marx and Engels contend that ideas are shaped by the material world, but as historical materialists they understand the material to consist of relations of production that undergo change and development. Moreover, for Marx and Engels, it is the exploitative and alienating features of capitalist economic relations that prompt ideas they dub ‘ideology.’ Ideology only arises where there are social conditions such as those produced by private property that are vulnerable to criticism and protest; ideology exists to protect these social conditions from attack by those who are disadvantaged by them. Capitalist ideologies give an inverted explanation for market relations, for example, so that human beings perceive their actions as the consequence of economic factors, rather than the other way around, and moreover, thereby understand the market to be natural and inevitable. Members of the Frankfurt School such as Jürgen Habermas drew on the Marxist idea of ideology as a distortion of reality to point to its role in communication, wherein interlocutors find that power relations prevent the open, uncoerced articulation of beliefs and values.