This paper is devoted to the analysis of Plotinus’ citation of the Heraclitean saying B113 DK in the second treatise On the Presence of Being (VI 5 [23]). I shall argue that the use which the author of the Enneads makes of this fragment has been hitherto misunderstood by scholars and that, for this reason, the significance of the passage and its role within Plotinus’ argument have been missed. Close attention will be paid to the tool through which Plotinus conveys (...) his own reading of Heraclitus’ tenet, i.e. etymology, and to the passages in which he both lays down and puts into practice the programmatic guidelines for his interpretation of the Presocratic. In addition, I shall interpret Plotinus’ recourse to a wordplay which is, in character, quite Heraclitean as a proof of the importance of his philosophical engagement with the Obscure. (shrink)