I find this sort of stylized symposium pretentious. This one, which seems to have taken place a few weeks back, hardly disappoints. But if you are the folks at SFMOMA you can do what you like. In any case, they hosted the event, inviting a baker's dozen of noted critics and commentators* to answer the question.
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* Vince Aletti, George Baker, Walead Beshty, Jennifer Blessing, Charlotte Cotton, Philip-Lorca diCorcia, Geoff Dyer, Peter Galassi, Corey Keller, Douglas Nickel, Trevor Paglen, Blake Stimson, and Joel Snyder. You can find their brief opening statements at the symposium web page.