we are a shadow's dream
Interesting. Since putting up that translation the first time, I've seriously revised my interpretation. It can't be the shadow that's dreaming (subjective genitive); it must instead be a dream about a shadow (objective genitive). And though ἄνθρωπος refers to all of us humans, Pindar is addressing a specific athlete, reminding him that, until the moment of glory arrives, he, like the rest of us, is "a dream of a shadow." So "you" (in of course a broad, generic sense) may be just as valid a translation as "we."