This chapter focuses on some of the most important religious influences on human behaviour: religious worldviews, beliefs, doctrines, and theologies. These aspects of religion provide a lens through which people can understand the world around them. Religions also include explicit instructions on how to behave. These qualities of religion, potentially, have profound influences on political behaviour. Jewish laws, known as halacha, include a complex and voluminous set of laws found in both the Old Testament and what was originally an oral tradition, but for the past two millennia the oral law has been written into hundreds, perhaps thousands, of authoritative volumes. Religious rules can constrain what actions combatants may take in conflict, regardless of whether the conflict itself has religious motivations. Similarly, as compared to religious identity or affiliation, belief is a more important determinant of political participation, attitudes toward foreign policy, and tolerance of other religions and ethnicities.