It is often argued that art is not necessarily aesthetic by way of using conceptual art as the counterexample to the aesthetic thesis. A typical argument is that Duchamp's readymades are art and yet Duchamp himself insisted that they have no aesthetic properties, therefore aesthetic properties are not necessary for art. (One article I am thinking of here is by Christy Mag Uidhir and Cameron Buckner "Portrait of the Artist as an Aesthetic Expert." in Aesthetics and The Sciences of the Mind Oxford, 2014) One way to address this is to argue that the readymades are not art. However, for the purposes of my comment, I'll assume that they are art. So the point I want to make is that readymades are art and that one of the things that makes them art is their aesthetic nature. Duchamp himself said that "Aesthetic delectation is the danger to be avoided" at least according to Arthur Danto. Does that prove the contrary point? The role of "delectation" may qualify the quote somewhat: the danger may be in delectation, not in the aesthetic as such. The term "delectation" comes from the 14th century for delight and enjoyment. However, it seems to serve an ironic purpose, since "for your delight" would be more efficient than "for your delectation." Delectation is something highfalutin.
In any case, let us consider some alternative ways to approach a readymade aesthetically, ways that do not focus overmuch on delight or any fancy sort of savory implied by "delectation." The key might be in the definition of "aesthetic experience." Here's a definition from Levinson, quoted in Sherri Irvin's "Is Aesthetic Experience Possible." It says "Aesthetic experience is experience involving aesthetic perception of some object, grounded in aesthetic attention to the object, and in which there is a positive hedonic, affective or evaluative response to the perception itself or the content of that perception." (Aesthetics and the Sciences of the Mind, 37) Aside from the problem that the term "aesthetic" is not actually defined here (maybe Levinson defines it elsewhere) the definition leaves open how to distinguish those positive hedonic, affective or evaluative responses to perceptions or their contents that are aesthetic from those that are not. My definition of the aesthetic in terms of aura (as set forth in my book) requires that the aesthetic experience be one of heightened significance in which the object seems more alive or real. Agreeing with Levinson, it should also be a positive hedonic, affective or evaluative response to perceptions or their contents. So, on this account, we do not have to have delectation to responds aesthetically to Duchamp's readymades. When such objects are appropriately perceived, i.e. in this case as art objects or at the very minimum as aesthetically interesting objects, they have aura. They have a power of fascination, not just in terms of finding the concept fascinating, but in finding the object itself so. They are placed in museums with the expectation that they can be perceived aesthetically.
Danto could be said to have argued that something is art if it is seen as and experienced as art by someone having appropriate art historical knowledge. (He never put his definition in this way, but this is a likely interpretation.) He also thought it must have some aspect which can only be seen in terms of the "is" of representation, by which he really meant (I admit I am reading this into him) that the object must be perceived as having heightened reality. We cannot but see Fountain aesthetically on my view if we see it under the appropriate concept of art. "This is Fountain" where the "is" is the "is" designated by Danto makes it not only art but also aesthetic. Fountain has the aura of "seen, quite surprisingly, as art." (Heightened significance can be achieved by the tension of something being on one level a paradigm under its prime concept and on another as an outlier or even excluded from the extension of the concept.) In presenting it to the world in the way he did Duchamp gives it this aura. So how can it not be aesthetic?
I think we philosophers too often forget that readymades are presented for aesthetic consideration. Consider the following point from Steven Goldsmith: "The formal principle behind the readymade
is far from revolutionary and harkens
back to Kant's notion of disinterestedness.
Wrench a common object from its
functional environment, eliminate its potential
for practical use, set it upon a
stand like objects traditionally devoted to
aesthetic scrutiny, and the formal design
previously obscured in the object is
thrown into the forefront of consideration.
Without the film of familiarity that hinders
us from seeing beyond its' function, a
urinal can become a highly polished,
gleaming artwork that combines masculine
piping with rounded feminine curves-not
unlike the androgenous figures created
by Henry Moore." "The Readymades of Marcel Duchamp: The Ambiguities of an Aesthetic Revolution" The Journal of Aesthetics and Art Criticism, 42: 2 (1983): 197-208. Goldsmith's actual thesis aside, the point I want to make is that in displaying the urinal as art Duchamp was setting his objects on the stand, not perhaps for aesthetic delectation, but to be experienced as with aura.