There is no such thing. Memory is always and only individual, and - as is well known - two people who witnessed, or participated in the same event, will have distinct memories of it, according to their respective roles, social positions, points of observation, previous prejudices, later influences, acquired knowledge and reevaluation. I am aware, of course, that this fashionable, almost obligatory notion of 'collective memory' is used as a metaphor, as a convenient term to denote a sum of convergent recollections, beliefs, feelings and judgements on the past that have been deposited in contemporaries' minds. Still it seems to me that this is a misleading metaphor, since it encourages us to slide over substantial differences in historical perception and understanding among members of one and the same nation, class or generation.