Aristotle in his will made him guardian of his children, including Nicomachus, with whom he was close. Aristotle likewise bequeathed to him his library and the originals of his works, and designated him as his successor at the Lyceum. Eudemus of Rhodes also had some claims to this position, and Aristoxenus is said to have resented Aristotle's choice.

Theophrastus presided over the Peripatetic school