Larry notes: >>> Well, "Platonic" has been around since 1533 and "Shavian" since 1904, and I don't see any signs of "Platon" or "Shav", so perhaps Rubens is safe from eviction by back-formation for a while longer. <<< But they are at least as well known by name as by adjective (ISTM), an advantage that P.P.R. hasn't got. mark by hand