In the history of a specific idea there are moments of reception that radically alter a concept’s functioning, moments where its meaning is transplanted in such a way that an internal rupture emerges. In the case of imagination the Neoplatonist Proclus (410/412-485) seems responsible for such a disruptive reception. Proclus is generally held to be the first to have systematically cut imagination’s exclusive ties with sense-data in his projectionist philosophy of mathematics, presented in his Commentary of the First Book of Euclid’s Elements (Bouriau 2002, 49). Proclus’ theory of geometry consists in a frontal attack on the traditional, Aristotelian viewpoint that geometry deals with sensible objects qua planes, qua lines, etc. From Aristotle’s point of view (Metaph. 1077b24-30), geometry ‘makes abstraction from’ or ‘leaves unconsidered’ the material composition of a specific object, by filtering out the properties of sensible objects that are not mathematically relevant. According to Proclus, in geometry discursive thinking uses imagined representations of innate concepts. Due to and within imagination these unextended ideas are projected as extended and divisible. Therefore the Neoplatonist is called, along with Descartes, a philosopher of the productive imagination (Bouriau 2002, 47; Rabouin 2009, 178), a term hardly compatible with the traditional, Aristotelian vocabulary. The compatibility of this productive geometrical imagination with imagination’s functioning in other contexts of the Neoplatonist’s oeuvre, where imagination is generally understood as the deceitful receptacle of the imprints from sensible objects, is a much debated topic. Nonetheless, imagination’s ambiguous and shifting meaning in the Proclean’ corpus is generally believed to be an interpretative problem. In the present article I will argue that by introducing imagination’s productive side and by simultaneously holding on to its traditional features, Proclus wittingly or unwittingly reveals a shift in meaning and functioning that was always already proper to imagination as a mediating place between sensibility and intelligibility, between productivity and reproductivity. For that reason, imagination’s ambiguous meaning throughout the Proclian corpus should not so much be considered an interpretative problem as a symptomatic manifestation of an underlying structure – a system