  To these criticisms several responses have been offered. First, the less restrictive conception of aesthetic properties mentioned above, on which they may be based on non-perceptual formal properties, can be deployed. On this view, conceptual works would have aesthetic features, much the same way that mathematical entities are often claimed to (Shelley 2003, Carroll 2004). Second, a distinction may be drawn between time-sensitive properties, whose standard observation conditions include an essential reference to the temporal location of the observer, and non-time-sensitive properties, which do not. Higher-order aesthetic properties like drama, humor, and irony, which account for a significant part of the appeal of Duchamp’s and Cage’s works, on this view, would derive from time-sensitive properties (Zemach 1997). Third, it might be held that it is the creative act of presenting something that is in the relevant sense unfamiliar, into a new context, the artworld, which has aesthetic properties. Or, fourth, it might be held that (Zangwill’s “second-order” strategy) works like ready-mades lack aesthetic functions, but are parasitic upon, because meant to be considered in the context of, works that do have aesthetic functions, and therefore constitute marginal borderline cases of art that do not merit the theoretical primacy they are often given. Finally, it can be flatly denied that the ready-mades were works of art (Beardsley 1982).