It is a well-known feature of the later Neoplatonist writings from the fifth century ad onwards that the authors frequently refer to their own philosophical teachers. The standard formula, which is almost invariably used on these occasions, is ho hēmeteros kathēgemōn (ὁ ἡμέτερος καθηγεμών, ‘our teacher’); it is attested about thirty times in Proclus, ten times in Simplicius and, with a lower frequency, in Damascius and others. The custom is not wholly unprecedented. Philosophers and medical writers from earlier in the Imperial age, such as Plutarch and Galen, sometimes use similar commemorative formulas, and there may even have been precedents in Hellenistic Epicureanism.