There is an ambivalence here: utopia fascinates as an expression of the felt problems and solutions of particular historical situations; it inspires as a response to the recurrent problems across history; yet it provokes fear that the revolutionary may make the mistake of taking it literally. There is an implied model of the process of social change, as well as its direction: ideas are the motive force in social progress, so that utopia must be taken seriously as a contribution to this – but not too seriously, or evolution and progress may turn to revolution and disaster. Levitas, The Concept of Utopia, p.9