When one man attacks, or robs, or attempts to murder another, all the neighbours take the alarm, and think that they do right when they run, either to revenge the person who has been injured, or to defend him who is in danger of being so.
 Adam Smith, The Theory of Moral Sentiments (1759). copy citation

Context

“Among equals each individual is naturally, and antecedent to the institution of civil government, regarded as having a right both to defend himself from injuries, and to exact a certain degree of punishment for those which have been done to him. Every generous spectator not only approves of his conduct when he does this, but enters so far into his sentiments as often to be willing to assist him. When one man attacks, or robs, or attempts to murder another, all the neighbours take the alarm, and think that they do right when they run, either to revenge the person who has been injured, or to defend him who is in danger of being so. But when a father fails in the ordinary degree of parental affection towards a son; when a son seems to want that filial reverence which might be expected to his father; when brothers are without the usual degree of brotherly affection;” source