A recent upsurge of empirical studies on the causes of conflict attempts to connect various features of the distribution of the relevant characteristic (typically ethnicity or religion) to conflict. The distributional indices differ (polarization, fractionalization or Lorenz-domination) and so do the various specifications of "conflict" (onset, incidence or intensity). Overall, the results are far from clear, and combined with the mixture of alternative indices and notions of "conflict" it is not surprising that the reader may come away thoroughly perplexed. The aim of this paper is to provide a theoretical framework that permits us to distinguish between the occurrence of conflict and its severity and that clarifies the role of polarization and fractionalization in each of these cases. Our analysis brings together strands from three of our previous contributions: on polarization (Esteban and Ray, 1994, and Duclos, Esteban and Ray, 2004), on conflict and distribution (Esteban and Ray, 1999) and on the viability of political systems (Esteban and Ray, 2001).Esteban gratefully acknowledges support from the Instituto de Estudios Fiscales, the Polarization and Conflict project CIT-2-CT-2004-506084 funded by the European Commission-DG Research Sixth Framework Programme, Barcelona Economics (XREA) and the CICYT grant no. SEC2003-01961.