  The existing evidence about Numenius suggests that he was strongly concerned with metaphysics. His metaphysical views can be distinguished into ontological and theological ones. The remains of his treatise On the Good show, however, that these two sets of views were closely linked together.  Numenius defines the subject matter of this treatise as an investigation of the question what is being (fr. 3.1, fr. 5.5, fr.  7.12–13), which is reminiscent of Aristotle's definition of first philosophy, or metaphysics, in Metaphysics Gamma (1003a20–32). Quite notably, however, Numenius declares that he will be guided in his investigation by the Timaeus (referring to Timaeus 27d-28a; fr. 7.8-12). In line with the Timaeus, Numenius treats the Good, the highest principle, as well as the lower principles of reality that he introduces, as gods.