These works were written against a background of war and racism. Freud sought the sources of conflict in the deepest memories of humankind, finding clear continuities between our ‘primitive’ past and ‘civilized’ modernity. In Totem and Taboo he explores institutions of tribal life, tracing analogies between the rites of hunter-gatherers and the obsessions of urban-dwellers, while Mourning and Melancholia sees a similarly self-destructive savagery underlying individual life in the modern age, which issues at times in self-harm and suicide. And Freud’s extraordinary letter to Einstein, Why War? – rejecting what he saw as the physicist’s naive pacifism – sums up his unsparing view of history in a few profoundly pessimistic, yet grimly persuasive pages.