''In the 14th century people are concerned with whether someone is of good or ill repute; it's a collective, community judgment. When you get into the 15th century, the question is about someone's 'governance.' There is a shift from community reputation to an emphasis on internal control.'' A proliferation of tracts and manuals on proper behavior trickle down to common, illiterate folks in the form of rhymes and ditties.One theory is that that the decline in resolving matters of honour through violent means was a result of the rising power of monarchs and states, and the ability of the state to enforce its laws more uniformly, removing the impetus for communities to take matters into their own hands. Others claim cultural shifts for the change:
Mr. Muir describes how the Republic of Venice tried to put an end to violent feuding among unruly nobles as it extended its influence into remote rural areas in the 17th century. The wars fought over generations by the area's leading families left the region vulnerable to foreign invasion. Venice reacted by first meting out stiff punishment, then by drawing the rural noble families into Venetian aristocratic life. Here they learned to replace the clan feud with the individual duel, an important shift from collective violence to individual responsibility and violence. Finally, the feuding clans, who now prided themselves on their courtly behavior, fought it out through the publication of dueling pamphlets, trying to best their rivals through elegant put-downs and masterly argument.
''Both the Protestant Reformation and the Catholic Counter-Reformation put a lot of emphasis on individual conscience,'' said Tom Cohen, who teaches history at York University in Toronto. ''The conscience becomes the internal gyroscope. There is the growth of introspection -- the diary, the novel, the personal essay. Along with the kind of personal self-control that Norbert Elias describes.''
Conversely, Mr. Roth noted, one sees significant increases in violence at times of political tension when the legitimacy of government is under serious attack, before and after the Civil War, as well as after World War I in Europe. The fact that murder rates did not go down in Italy and Greece until the 19th centuries, when each country won its political independence and formed a modern national state, suggests that the decline may have had more to do with state formation than with the trickling down of court culture.
Revenge killing seems to correlate with what sociologists call cultures of honour: ones where one is obliged to defend one's (and one's family's) honour and demonstrate that one is a tough guy. I've seen claims in a number of places that the reason the US South's murder rate is twice that of the North is because it inherited the culture of honour of the Scottish borders/northern Ireland. The Scotch-Irish culture of honour, in turn, was shaped by relatively lawless regions and the need to defend against cattle rustlers and thieves. Which ties into the weak-state hypothesis.
The prominent evolutionary psychologists Martin Daly and Margo Wilson went into this topic in some detail in their 1988 magnum opus "Homicide". There is a lot of detail and I don't know if I can summarize their reasoning into a simple "cause" of the decline in homicide rates but they seem to support the "rise of the state" model. The chapter on the history of revenge killing is probably the most relevant. They describe the situation in medieval England and how this practice declined with the growth of the rule of law. Being evolutionists they are not content to simply invoke "cultural change" but analyze the pros and cons of different courses of action from the individual's point of view. I haven't looked up the historians quoted in the NYT article but it would be interesting to know whether they are citing Daly and Wilson.