A well known problem in understanding the scriptural exegesis of Basil of Caesarea is how to account for the apparent contradiction between his Origenist exegesis (in his homilies on the Psalms, for example) and his literal exegesis and criticisms of allegory in his masterpiece, the Hexaemeron. Various explanations have been offered by scholars, such as that Basil changed his point of view late in life, moving more toward "Antiochene" exegesis, or by downplaying Basil's association with Origen and his hermeneutics in the first place. Richard Lim, in an important article, criticized these explanations, instead arguing for continuity between Origen and Basil. He did so by asserting both that Basil's rejection of allegory in the Hexaemeron was limited only to what Lim termed "translational" allegory (that is, allegory that rejects the literal sense) and that the literal method of interpretation used in it was suited to its allegedly uneducated audience. Although Lim is right to reject previous scholarly explanations and maintain the connection between Basil and Origen, neither of his arguments is sustainable. I argue that a better explanation for Basil's different interpretative method in the Hexaemeron lies in his understanding of Genesis 1 as a privileged source of cosmology, which he must defend against Gnostic cosmologies. Because the Gnostics use allegorical explanations of Genesis 1 to support their dualistic cosmology, Basil must insist on the reasonableness and sufficiency of the text at the literal level.