This contribution to the debate on museum collecting and disposal takes as its starting point the results of a survey which demonstrates that museums are continuing to collect at a significant rate, and that disposal is not being used as a collections management tool. Museums are therefore currently unsustainable institutions, which pass on their expanded collections in a way that increases the management burden for future generations. In order to address this problem, it is argued that disposal must have a significant role to play in collections management. It is still rarely used because a professional reticence over the issue has developed, both through decades of training which has instilled a "presumption against disposal", and because nearly all disposals have been done on pragmatic grounds of saving costs or space, with no coherent intellectual framework within which to justify them. What is needed is a review of the philosophy underpinning museum collecting and an examination of whether it still serves us well. The literature on cultural heritage and the anthropology of memory provides a framework for challenging the notion that museums still function as repositories of objects and specimens that represent an objective record or collective memory. Instead, they should be seen for what they are: partial, historically contingent assemblages that reflect the tastes and interests of both the times and the individuals who made them. The intellectual framework put forward allows us not to be solely beholden by the collecting decisions of our predecessors, but to re-work these object "memories" and to choose to "forget" some of them through disposal. Finally, some of the practical implications of this framework are examined. It does not mean that museums can dispose of anything they choose, but it does mean that, instead of treating all collections as having equal importance, the ascription of value must become a fundamental part of curatorship. A number of existing schemes that do this are summarized, and some prospects for future development are outlined.