Only as good using the usual large margins for error people use when judging art.  E.g. I'm willing to say that Leonardo was better than Parmigianino.  I'd think twice before saying he was better than Rembrandt.  Or vice versa.<p>This isn't some idiosyncracy of mine.  Most art historians make comparisons at about that level of precision.<p>I'm willing to concede the point on anything that (a) I actually wrote, and (b) that's been refuted. E.g. I pointed out what I actually wrote, and invited you to refute it here: <a href="http://news.ycombinator.com/item?id=985662" rel="nofollow">http://news.ycombinator.com/item?id=985662</a><p>Though you claim to be an expert in art history, mistakes on the scale of the one I quoted in the link above make me think you haven't studied it as thoroughly as I have.  I'm not trying to be snarky by emphasizing your mistakes; there's just no other way for the "technical people" you mention to decide who to believe.<p>It's actually an interesting question which fields are cumulative, and to what degree, and why they differ.  E.g. math is entirely so, which is why I'd be very reluctant to compare different mathematicians from different eras.  Whereas progress in the "soft" sciences is less cumulative, and in the arts much less.