See http://documents.worldbank.org/curated/en/359271468739530199/pdf/multi-page.pdf for Paul Collier and Anke Hoeffler’s views on ‘greed’ versus ‘grievance’ as a cause of civil war.

Robert A. Hinde, The Psychological Basis of War http://www.unc.edu/depts/diplomat/AD_Issues/amdipl_7/hinde.html is another useful source on the psychological causes of war.

David Keen looks at the links between ‘greed’ and ‘grievance’ in http://eprints.lse.ac.uk/44901/.