A culture can be expressed in a succinct way in its rituals, the manifestations of the culmination of its deepest beliefs. Rituals are also attempts to maintain cohesion, which they do most successfully in the material and non-material arts. Knowledge of a culture is necessary in order to portray the totality of that culture through its rituals and ceremonies. As a central topic in anthropology, ritual has been regarded as a phenomenon that is resistant to change and bound to a great extent to certain norms and regulations. Yet it is obvious that rituals are not rigid, unvarying sets of performances and that they have undergone many changes in definitions, functions and interpretations. Indeed, all aspects of culture, including rituals, are subject to change. Drawing on the past, cultures sustain their beliefs by making use of what is at hand in the present.