The Italian Jesuit theologian Robert Bellarmine, when teaching at the Jesuit College in Louvain (1570-76), proposed a hypothesis that God might have created the first man in a purely natural state and have not elevated human beings to the supernatural end. The hypotheis should be read in the context of Bellarmine’s efforts to correct the Louvain theologian Baius' teaching on Adam's grace. For Bellarmine, the hypothetical man in puris naturalibus helps to explain the gratuity of God's grace granted to Adam at the beginning of his existence. Taking a historical perspective, we find that Bellarmine is not the creator of the theology of pure nature. His theology of pure nature is a synthesis of the theological tradition in the preceding centuries.