This article critically explores the history and nature of a hermeneutic assumption which frequently guided interpretations of Plotinus from the 18th century onwards, namely that Plotinus advanced a system of philosophy. It is argued that this assumption was introduced relatively late, in the 18th and 19th centuries, and that it was primarily made possible by Brucker’s methodology for the history of philosophy, dating from the 1740s, to which the concept of a ‘system of philosophy’ was essential. It is observed that (...) the concept is absent from Ficino’s commentary from the 15th century, and that it remained absent in interpretations produced between the 15th and 18th centuries. It is also argued that the assumption of a ‘system of philosophy’ in Plotinus is historically incorrect—we do not find this concept in Plotinus’ writings, and his own statements about method point in other directions. Eduard Zeller is typically regarded as the first to give a satisfying account of Plotinus’ philosophy as a whole. In this article, on the other hand, Zeller is seen as having finalised a tradition initiated in the 18th century. Very few Plotinus scholars have examined the interpretative development prior to Zeller. Schiavone and Bonetti , for instance, have given little attention to Brucker’s introduction of the concept of a ‘system of philosophy’. The present analysis, then, has value for an understanding of Plotinus’ Enneads. It also explains why “pre-Bruckerian” interpretations of Plotinus appear alien to the modern reader; the analysis may even serve to make some sense of the hermeneutics employed by Renaissance Platonists and commentators, who are often eclipsed from the tradition of Platonism. (shrink)