The epithet "do-gooder" is often used about those who work in charities and voluntary organisations. Sometimes it is spoken with a sneer, as if there is something wrong with do-gooders; even when said in a positive way, the tone can be less than wholehearted.
The great fictional lampoon of the do-gooder is in Dickens: the eyes of Mrs Jellyby in Bleak House are so fixed on the distant work of her Africa project that she fails to notice her children falling down stairs or getting their heads stuck in railings.
This book, however, is more ambitious: it combines a sympathetic examination of what do-gooders are like in real life with a detailed analysis of attitudes towards the moral, philosophical and psychological aspects of do-gooding in history.
The examples include Dorothy Granada, a nurse in Nicaragua during revolutionary times, defying the Contras to continue her work with poor women; Aaron Pitkin, who has devoted his life to the welfare of chickens in the US; and Baba, a Brahmin Indian princeling who founded and ran a leper colony.
The analysis explores, with reference to Kant, the utilitarians, Adam Smith, Darwin and Freud, whether do-gooding is normal or pathological, and whether there is a connection between altruism and masochism or narcissism.
Larissa MacFarquhar, a staff writer on The New York Times, concludes that do-gooders are different: they are prepared to prioritise the needs of strangers above their own lives and their families, and this can bring both benefit and destruction, depending on choice and luck.
The world would cease to function if we were all do-gooders, focused exclusively on relieving the pain of strangers, she says; but it would also be a worse place without these "strange, hopeful, tough, idealistic, demanding, life-threatening and relentless people".
Strangers Drowning, by Larissa MacFarquhar, published by Allen Lane, £20 hardback