All modern studies concerning the authenticity of Prometheus Bound, as well as passing references to the issue, trace this thorny question back to the mid-nineteenth century. In this study we will attempt to show that at least the notion of Prometheus as a drama deviating from the rest of the Aeschylean production is in fact much older, and therefore the conception of this idea can now be backdated. More specifically, Michael Psellos, an erudite scholar of eleventh-century Byzantium, in a comparative treatise on the versification of George of Pisidia and Euripides, makes a condensed comment about Prometheus, which adumbrates the current argument against the Aeschylean origin of the drama. The main purpose of this paper is to ascertain why, and also in what way, does Psellos question, not the authenticity of course, but the typical nature of a renowned composition, traditionally considered to be part of the Aeschylean canon. By bringing Psellos’ reference about Prometheus to the fore, we can now establish this Byzantine scholar as the first questioning voice as regards the un-Aeschylean nature of the disputed play, and the eleventh century ce as the historical time in which this kind of pondering was expressed for the very first time.