 The assumption in question is, then, that although we seem to gain something from looking at, for example, a postcard or poster of Katsushika Hokusai's Fine Wine, Clear Morning or Élisabeth Vigée Le Brun’s Self-Portrait in a Straw Hat , a genuine judgement about its artistic character necessitates one’s own un-mediated perceptual experience of it. But – and herein lies the crux of the problem for conceptual art – what if there is nothing for us to get a first-hand perceptual experience of? In the case of Walter De Maria’s Vertical Earth Kilometer  (1977)[6],  a kilometre-long metal shaft plunged into the surface of the earth so that only the very top is visible, first-hand perceptual experience is simply not something that can be had. More pertinently, what does it even mean to have a perceptual engagement with an artwork that claims, basically, to be an idea?