If you'd muddy your clothes to save a drowning child, why not to save a child far away?

Because Peter Singer argued that there is no morally relevant difference, and he built the case on a child in a pond. In his essay "Famine, Affluence, and Morality", written in 1971 and inspired by the starvation of Bangladesh Liberation War refugees, he argues that affluent people are obligated to give far more to humanitarian causes than is normal in Western cultures.

The argument starts from the drowning child. Inaction is clearly immoral if a child is drowning in a shallow pond and you could save them but choose not to; getting your clothes muddy is not of comparable moral importance. Singer's principle generalizes: if it is in our power to prevent something bad from happening without sacrificing anything of comparable moral importance, we ought, morally, to do it. And it makes no moral difference, he says, whether the person you can help is a neighbour's child ten yards away or a stranger ten thousand miles away.

The reply that follows is the demandingness objection: if that is true, morality asks for far too much. Singer's answer is to accept it. The question, he says, is not what we usually do but what we ought to do, and he sees no sound moral justification for the view that distance or community membership makes a crucial difference to our obligations.

Others push back with variations of the pond. Kwame Anthony Appiah asked whether the man in the expensive suit should sell it and donate the money rather than save the child and ruin it, and he believed he should save the child and ruin the suit.