The positive valuation of theatre as live performance, and therefore also its transience, is frequently accompanied by the urgent expression of the need to counter that transience by means of documentation. This desire to ‘save’ theatre reaches its most fervent expression (and hope of authority and permanence) with the live performance archive. Archive theory, however, now insists on the instability and uncertainty of the archive, which not only documents but also constructs its subject. In this article, Matthew Reason argues that, by tracing comparisons between archives and human memory, it is possible to establish a new formulation of the archive – as detritus, not completeness – that puts a value on mutability as a reflection of theatre's liveness. Matthew Reason is currently completing a PhD on representations of live performance at the University of Edinburgh. He has edited a special edition of the Edinburgh Review (ER106) on Theatre in Scotland, and has previously worked at the Edinburgh International Festival, where his responsibilities included maintaining the archive.