For some decades now the term ‘Ideology’ has been used in a variety of senses. Recently, some on the whole cursory discussion of the meaning of the term has flared up, especially in conjunction with the post-war evaluation of totalitarianism and the correlative debate about the end of ideology. Yet the problem of an adequate definition and uniform usage of the term is still with us. The definitions which are in use and which, if defended at all, are defended rather by assertion than demonstration, can be divided into two main categories. One may be called the restrictive conception, because it confines the concept to specific political belief systems. The other category of definitions may, I suggest, be designated the inclusive conception, since according to it ‘ideology’ is applied to all political doctrines. In the context of social and political theory and science, this usage means that the concept covers sets of factual and moral propositions which serve to posit, explain and justify ends and means of organized social action, especially political action, irrespective of whether such action aims to preserve, amend, destroy or rebuild any given order. According to this conception, ideology is as inseparable from politics as politics from ideology.