High levels of religiosity have been linked to lower levels of intelligence in a number of recent studies. These results have generated both controversy and theoretical interest. Here in a large sample of US adults we address several issues that restricted the generalizability of these previous results. We measured six dimensions of religiosity (rather than just one or two), along with a multi-scale instrument to assess general intelligence. We also controlled for the influence of the personality trait openness on facets of religious belief and practice. The results indicated that lower intelligence is most strongly associated with higher levels of fundamentalism, but also modestly predicts central components of religiosity such as a sense of religious identification and private religious practice. Secondly, we found that a higher level of openness – often assumed to lead to lower religiosity – is weakly associated with reduced fundamentalism but with increased religious mindfulness, private religious practice, religious support, and spirituality. These new results provide a framework for understanding the links between reasoning and faith.