In spite of over fifty years of curriculum theorising on the part of those who have consciously set out to develop curriculum theory, and centuries of thought devoted to wider problems of the nature of education, fundamental questions of the purposes and concepts that should characterise curriculum theory are still matters of lively contention. That this is the case is a matter of concern not only to philosophers and theoreticians, but also to all those responsible for and affected by practical decision-making on the curriculum. At a time when, all over the world, there is massive intervention on the part of governments in the shaping of school curricula, questions of how we conceptualise curriculum tasks assume a special importance: intervention is never atheoretical ~ it always implies some view of what the curriculum is and what theories and metaphors should guide its planning. The theory of rational curriculum design expounded by Tyler and others is, perhaps, the outstanding example of a conceptualisation that has exerted, and continues to exert, a profound and world-wide influence on the nature of curriculum decision-making.