1. Do you have to be able to sit on a “chair” for it to be considered a chair? Is a broken chair not a chair anymore? This stuff makes my head hurt. If you have to meet the requirement of the definition, then only the wooden chair is a chair, because the definition and photograph do not have four legs and a back to support one person. A horse has four legs and a back and I can sit on it – is a horse a chair? What about a tiny doll’s chair? Technically I could sit on it but it would not support me. All “chairs”, whether actual physical items, or any artists’ versions (photograph, painting, sculpture…), or the idea of a chair in the form of a definition are all chairs. And because the definition of a chair can spark different ideas for each person, there are an infinite number of chairs in Kosuth’s artwork.
2. I think that Plato would say that the definition is the real chair. It represents the original idea, and is closest to the “one existing in nature, which is made by God.” Only the idea is pure. And because “no artificer makes the ideas themselves”, he believes all makers are imitators; anyone can make any version and still fit the idea. So the carpenter who made the chair made “only some semblance of existance.” Because there can be an infinite number of versions, Plato believes that none of them are truly real. And the photographer is just imitating the imitation of the definition, just like the “painter…. a creator of appearances.”