On Selfhood and Godhood is primarily concerned with laying the foundation for the practice of natural theology within a rationalist framework. Campbell's first approach to his subject is an attempt to define the self as a moral agent in order to demonstrate implicitly reasonable grounds for theological language regarding the soul. In the second half of the work, Campbell investigates the possibility of an objectively verifiable Theism, building parallels between the moral systems discussed in the first half and the religious systems under consideration in the second. Campbell is eventually forced to abandon the idea of a purely rational Theism and investigate the supra-rational idea of the numinous as posited by Otto; the conclusion of the work is based on a reconciliation between this and a more traditional philosophical vocabulary.