Blowing the whistle on liars, cheaters, or thieves is likely to impose a cost on the whistle-blower, while everyone else benefits from this act of conscience. If this is so, then why don't people just mind their own business and let someone else do the dirty work? A conceivable explanation is that if no one else perceives the transgression or, similarly, if no one else is willing to do anything about it, then perhaps the miscreant will get away with it, whereupon everyone will be worse off. Another explanation--one of particular interest to evolutionists-- is that people are, at least on occasion, inclined to do things that are detrimental to their personal benefit so long as their actions are sufficiently beneficial to the larger social unit. This action, which boils down to reconciling personal selfishness with public benefit, has occupied many of the great thinkers in social philosophy. These days it also drives empirical research--albeit mostly based on survey reports or laboratory simulations--while also tickling the imagination of evolutionary biologists, whether theory-minded or field-oriented. It also bears a complicated and as yet unresolved relationship to the fraught matter of honor-code violations, not only what motivates the perpetrators, but also what inspires those who turn them in. In this article, the author examines the biology of integrity and discusses how beneficent acts are biologically generated by a payoff enjoyed by a group, of which the altruist is often a member.