Proposals are being considered for a memorial on the site of the World Trade Center. Such competitions are necessarily good, writes Christopher Benfey. “In the end, we’re likely to get a celebrity sculptor who burnishes his or her reputation with an idiosyncratically designed?and inevitably ‘controversial’?monument. Or a sentimental and crowd-pleasing idea like the ‘soaring’ memorial envisaged by former Mayor Rudolph Giuliani. So, I have a simple proposal. My proposal is that we put nothing at all in that space?that it be left as a hollowed-out void.”