This dissertation is a work of multidisciplinary comparative philosophy of religion. It comprises a philosophical analysis and evaluation of Western traditions of philosophy and theology around the issue of religious anthropomorphism. More specifically, this study focuses on the tradition of Neoplatonic onto-theology in Western thought, and the divide in this tradition over the question of religious anthropomorphism and the divine nature. The dissertation frames this divide in terms of the distinction between an “anti-anthropomorphic” conception of the divine nature on the one hand, and an “attenuated anthropomorphic” conception of the divine nature on the other. Chapters two and three analyze key figures and texts from the “attenuated anthropomorphic” and “anti-anthropomorphic” traditions of Neoplatonic onto-theology. The fourth chapter considers a significant critique of this tradition as a whole leveled by Karl Barth and Martin Heidegger, among others, namely, that the onto-theological project as such constitutes a form of conceptual anthropomorphism. The fifth chapter provides an overview of the multidisciplinary scientific field known as the “bio-cultural study of religion,” which has yielded compelling evidence that anthropomorphic religious ideas are maturationally natural, culturally adaptive in certain past cultural contexts, and thus may reflect human cognitive limitations. The final chapter incorporates evidence from the BCSR (bio-cultural study of religion) in a comparative philosophical evaluation of the debates within and around the traditions of Neoplatonic onto-theology. The central philosophical thesis of this dissertation is that evidence from the BCSR negatively impacts—without decisively undercutting—the plausibility of the “attenuated anthropomorphic” tradition relative to the “anti-anthropomorphic” tradition. It does so by demonstrating that the anthropomorphic attributions inherent to the attenuated anthropomorphic view are undergirded by hypersensitive cognitive mechanisms, which are prone to misfiring. However, the BCSR also indicates several important weaknesses of the anti-anthropomorphic tradition of Neoplatonic onto-theology with regard to the social viability of this tradition. The BCSR also erodes the plausibility of the critique that onto-theology is itself a form of gross conceptual anthropomorphism. It does so by demonstrating that abstract onto-theological concepts lack the conceptual and cognitive liabilities inherent to the type of religious anthropomorphism advocated by Barth and Heidegger.