Social scientists have long recognized and sought to explain a connection between religious and political beliefs. Our research challenges the prevalent view that religion and politics constitute separate but related belief sets with a conceptual model that suggests the correlation between the two may be partially explained by an underlying psychological construct reflecting first principle beliefs on social organization. Moreover, we also push this challenge further by considering whether part of the relationship between political and religious beliefs is the result of shared genetic influences, which would suggest that a shared biological predisposition, or set of biological predispositions, underlies these attitudes. Using a classic twin design on a sample of American adults, we demonstrate that certain religious, political, and first principle beliefs can be explained by genetic and unique environmental components, and that the correlation between these three trait structures is primarily due to a common genetic path. As predicted, this relationship is found to hold for social ideology, but not for economic ideology. These findings provide evidence that the overlap between the religious and the political in the American context may in part be due to underlying principles regarding how to understand and organize society and that these principles may be adopted to satisfy biologically-influenced psychological needs.Key words: Behavior genetics; religion and politics; twin study; ideologyThe data employed in this project is publicly available and collected with the financial support of the National Science Foundation in the form of SES-0721378, PI: John R. Hibbing; Co-PIs: John R. Alford, Lindon J. Eaves, Carolyn L. Funk, Peter K. Hatemi, and Kevin B. Smith, and with the cooperation of the Minnesota Twin Registry at the University of Minnesota, Robert Krueger and Matthew McGue, Directors. Rather than thinking about religious beliefs influencing political attitudes through an intentional cognitive process (e.g. The Bible says homosexuality is wrong, therefore I oppose gay marriage) or political attitudes leading to changes in religious affiliation upon entering adulthood (Putnam and Campbell 2012), this study examines whether these belief systems overlap at least in part because they both represent an individual's preferences for "bedrock principles of group life," such as a preference for maintaining traditional moral values in society (Smith, Oxley, Hibbing, Alford and Hibbing 2011b). Our research challenges the prevalent view that religion and politics constitute separate but related belief sets with a conceptual model that explains both political and religious beliefs as rooted in the same underlying psychological construct reflecting first principle beliefs on social organization. Moreover, we also push this challenge further by considering whether part of the relationship between political and religious beliefs is the result of shared genetic influences, which would suggest that a shared predispo...