In Aëtius 1.7.8 Mansfeld–Runia, Diogenes, Cleanthes and Oenopides are said to have maintained that the deity is the world-soul. However, the identity of the Diogenes whom the doxographer mentions here has long been a matter of scholarly dispute. In response to attempts to ascribe the doxa to Diogenes of Apollonia, this paper reassesses old arguments and proposes new considerations to argue that a fundamental aspect of Diogenes of Babylon's theology is at stake here.