Irving Sandler suggested that John Cage was, apart from everything else he was, 'arguably the most influential critic/theoretician of the second half of the twentieth century'. Sylvester became interested in Cage's work and interviewed him twice (1966 and 1987), as well as writing about his work.
That Sylvester took an interest in Cage is not surprising- Cage's links to artists such as Johns and Rauschenberg played a part, as did his visual arts background and the visual appeal of his scores (the subject of an essay by Sylvester). But what is more interesting is the challenge to Sylvester's own position that represented, because as he stated in a radio discussion in the early 1970s, Sylvester needed the filter of an artist's intelligence to stimulate him. The example he gave was that he couldn't find a fork as found, as interesting as one presented or represented in the terms of an artwork. I expect that a fairly high percentage of those interested in contemporary art would be sympathetic to this view, because of the sense of a discussion or exchange which comes with it.
The irony of Cage's work is that it seeks to undo itself. It is a body of work created by an individual that is dedicated to breaking down the barriers between itself and everything outside itself. As Sylvester wrote of him,
'he is trying to create art that operates like nature- that leaves us to operate on it as we have to on nature. To look harder than art demands because art presents us with a vision, with nature we have to use our own'.
Experiencing Cage's art might then implicitly critique its audience, like an advertisement for a gym on TV. But in the unpublished text from which the above is taken, Sylvester seems to find Cage's work as containing pathos rather than the direct challenge of some of his contemporaries. What I think Sylvester takes from Cage's work is a temporary absorption in nature. In experiencing Cage's work we might have that feeling of being more aware of our surroundings, and wonder why we aren't always (or at least more often) in that state. But soon after the performance ends we go back to normal.
Sylvester was conscious of the way in which art focussed his attention, and wondered what would happen 'if we all went fishing and none of us made works of art'. This again chimes with the interview in which Cage reports that Johns had told him 'that he could imagine a world without any art in it and that he saw no reason for thinking that it would not be a better world than the one we're living in'. The paradox is that it's knowing what we get from art that makes us think that we should be able to get along fine without it.