Who's perspective matters: the artist's or the audience's?

According to John Cage, the audience can be the artist, or at least a large contributor to the artwork. He says that art "conforms to no rules. Not even its own" (93). I agree that there are no rules and anything can be argued to be a piece of artwork. The question that arises is: who decides the role played in the creation of that piece? John Cage can say that the noises the audience makes can be part of the performance. Yet, if the audience denies that they are artists or performers, was there any art in the first place? I believe there is no right or wrong to this question. If an artist (John Cage) has a pianist play...well, nothing...and thinks he has created art, then he has. If someone drops a cup of juice on the ground and another person sees a beautiful design and calls it art...it is. Any person interacting with the so-called artwork that finds it to be a creative piece can name it so, no matter which side of the canvas, stage, or screen they are on. And if someone says something is not art, then in their own mind it is not; however, as long as one person acknowledges it as being a creative composition, then it cannot be denied. If it exists for one, it exists.