Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Excellent theory of the origin of war

This is an outstanding reference for those seeking to understand how war came about and especially whether all societies were and are prone to war. Kelley presents a rigorously logical exposition of the notion that war is relatively recent and a result of social organization. All societies kill, but only those that are segmented and labeled appear to engage in large scale planned violence. Sometimes his conclusions are counterintuitive - as when he argues that, rather than scarcity, it is abundance that leads to war: "...it is under the latter circumstances that that a society can afford to have enemies for neighbors." While the prose can be somewhat dry at times, the reader is rewarded with numerous thought-provoking insights that are missing in watered down accounts of war intended for the general audience.