Are you a good person?

The proper answer to that question is, of course, “Go away.”

But you might reply that it depends on how one defines the word good. In a world of easily identified devils — Osama bin Laden, Kim Jong-Il, Bernard Madoff — most of us feel we’re basically on the side of the angels. We work hard, pay our bills, try to raise our children well, volunteer a bit here and there and, when in doubt, abide by the golden rule. (Don’t we?) Why not give ourselves the benefit of the doubt?

Peter Singer’s new book about world poverty, “The Life You Can Save,” is here to tell us that we aren’t, most of us, the people we think we are. On a planet full of so much obvious and widespread suffering, he writes, “there is something deeply askew with our widely accepted views about what it is to live a good life.”

In the third century BC, when Roman ambassadors were negotiating with the Greek city of Tarentum, an ill-judged laugh put paid to any hope of peace. Ancient writers disagree about the exact cause of the mirth, but they agree that Greek laughter was the final straw in driving the Romans to war.

One account points the finger at the bad Greek of the leading Roman ambassador, Postumius. It was so ungrammatical and strangely accented that the Tarentines could not conceal their amusement. The historian Dio Cassius, by contrast, laid the blame on the Romans’ national dress. “So far from receiving them decently”, he wrote, “the Tarentines laughed at the Roman toga among other things. It was the city garb, which we use in the Forum. And the envoys had put this on, whether to make a suitably dignified impression or out of fear – thinking that it would make the Tarentines respect them. But in fact groups of revellers jeered at them.” One of these revellers, he goes on, even went so far as “to bend down and shit” all over the offending garment. If true, this may also have contributed to the Roman outrage. Yet it is the laughter that Postumius emphasized in his menacing, and prophetic, reply. “Laugh, laugh while you can. For you’ll be weeping a long time when you wash this garment clean with your blood.”