 This leads to a set of ideas about how spectators measure success and, in particular, what they are able to say about performers, sets, and overall mise-en-scène, when they detect failures. If a spectator is unaware of a convention—a sequence of choices governed by some overall goal—as a convention, and if the presence of that convention is responsible for the aspects of the work that are present to be appreciated, then that spectator simply cannot appreciate that work, at least not for those aspects. This is partly because appreciation depends on having some level of understanding of what one is experiencing. Understanding requires spectators to offer hypotheses regarding what performers are up to in a performance, to test those hypotheses against the actual details of the performance, usually as it unfolds, and to assess the achievement the performance manifests given its aims and its context. Only spectators who understand performances and their features are able to offer the relevant kinds of hypotheses.