This thesis argues that Dio Chrysostom’s self-identification as a philosopher mattered a great deal more than what previous scholarship had suggested. Against the cultural and intellectual atmosphere of the first two centuries CE, it is argued that Dio had deliberately chosen to identify as a philosopher in his public activity in order to position himself at the apex of the intellectual pyramid. It is shown that Dio mixed philosophy, especially the public philosophy of Socrates and Diogenes, and the public speech, instead of the intimate dialogue, and that by doing so Dio had fashioned for himself – and as a legacy – a new model of public intellectual: a philosopher who is active in the public, civic space, and who intervenes in the political lives of cities by virtue of his identification as a philosopher. Instead of being a teacher, or a writer, like many other philosophers of his time, Dio urged philosophers to step out onto the public space and become active moral and political guides for their communities.