Full Idea
During and immediately after the war [14-18], those who hated the Germans were happier than those who still regarded them as human beings, because they could feel that what was being done served a good purpose.
Gist of Idea
In wartime, happiness is hating the enemy, because it gives the war a purpose
Source
Bertrand Russell (An Outline of Philosophy [1927], Ch 22)
Book Reference
Russell,Bertrand: 'An Outline of Philosophy' [Routledge 1979], p.186
A Reaction
A striking remark. There are lots of situations where hatred seems to increase happiness. Russell is roughly defending consequentialism.