entitled On the End: in Answer to Plotinus and Gentilianus Amelius. It opens with the following preface:
In our time, Marcellus, there have been many philosophers especially in our youth for there is a strange scarcity at present. When I was a boy, my parents' long journeys gave me the opportunity of seeing all the better-known teachers; and in later life those that still lived became known to me as my visits to this and that city and people brought me where they happened to live.
Some of these undertook the labour of developing their theories in formal works and so have bequeathed to the future the means of profiting by their services. Others thought they had done enough when they had convinced their own immediate hearers of the truth of their theories.
First of those that have written.
Among the Platonists there are Euclides, Democritus, Proclinus the philosopher of the Troad, and the two who still profess philosophy at Rome, Plotinus and his friend Gentilianus Amelius. Among the Stoics there are Themistocles and Phoibion and the two who flourished only a little while ago, Annius and Medius. And there is the Peripatetic, Heliodorus of Alexandria.
For those that have not written, there are among the Platonists Ammonius and Origen, two teachers whose lectures I myself attended during a long period, men greatly surpassing their contemporaries in mental power; and there are the Platonic Successors at Athens, Theodorus and Eubulus.
No doubt some writing of a metaphysical order stands to the credit of this group: Origen wrote on Spirit-Beings; Eubulus commented on both the Philebus and Gorgias, and examined the objections urged by Aristotle to Plato's Republic; but this is not enough to class either of them with systematic authors. This was side-play; authorship was not in the main plan of their careers.
Among Stoic teachers that refrained from writing we have Herminus and Lysimachus, and the two living at Athens, Musonius and Athensus; among Peripatetics, Ammonius and Ptolemaeus.
