At their first meeting, Porphyry took Plotinus for ‘a complete fool’ and a sophist. This reaction was by no means exceptional.1 The leading Platonists of the time, most notably Longinus, misclassified Plotinus as a representative of an Oriental, Pythagoreanizing version of Platonism.2 Admittedly, it was not easy to understand the novelty of his views. At stake in the discussions with Porphyry and Longinus was the claim that the intelligibles are not outside the Intellect. Marginal as it might appear at first sight, Plotinus’ thesis actually paved the way to a new interpretation of Plato’s Forms, the kernel for any Platonist system. After an intense exchange, Porphyry ‘finally managed to understand what he was saying’,3 wrote a retraction, and became one of his most faithful pupils for the years to come. Most of the other Platonists, however, continued to endorse their traditional interpretation. But in the meantime, the history of ancient Platonism had entered a new phase.