The broader conceptual context within which the twin vocabularies of history and of memory take on meaning is that of discourse on the relationships of past to present in human societies. John Lukacs writes of history as 'the remembered past', Peter Burke of 'history as social memory', Patrick Hutton of 'history as an art of memory'. Tensions can arise at the point between the idea of history as memorialization or witness and other conceptions of what history ought to be about. Shifting conceptions of the history-memory relationship form part of broader shifts and contests in cultural values. The 'historical past', R. G. Collingwood concluded, is 'not a remembered past, nor a sum of remembered pasts', but an 'ideal past', a past that has been organized through the workings of a constructive analytical imagination.