 To investigate the first principles of nature, Theophrastus depended on various observations of natural phenomena as well as on existing theories by earlier and contemporary thinkers, which are presented in this treatise sometimes in a sketchy manner and sometimes in more detail. In the case of the Academy, for instance, we find allusions to important metaphysical views introduced by Plato, but also by Speusippus and Xenocrates. These references cannot be said to constitute mere doxography, since they seem to have served the purposes of a dialectical examination. Theophrastus subjected the views of other philosophers to a series of objections and criticisms, while he avoided making definitive assertions; this gives the whole treatise an aporetic character, which has been compared both with Aristotle’s Metaphysics B, but also with the style of Metaphysics A.