Prehistoric warfare
The existence — and even the definition — of war in humanity's hypothetical state of nature has been a controversial topic in the history of ideas at least since Thomas Hobbes in "Leviathan" ( 1651 ) argued a "war of all against all" , a view directly challenged by Jean-Jacques Rousseau in a "Discourse on Inequality" ( 1755 ) and "The Social Contract" ( 1762 ) . 
<triplet> Thomas Hobbes <subj> "Leviathan" <obj> notable work <triplet> "Leviathan" <subj> Thomas Hobbes <obj> author <triplet> Discourse on Inequality <subj> Jean-Jacques Rousseau <obj> author <triplet> The Social Contract <subj> Jean-Jacques Rousseau <obj> author