The concept of modernity has long been central to legal theory. It is an intrinsically temporal concept, expressly or implicitly defined in contrast to pre-modernity. Legal theorists sometimes draw comparisons between, on the one hand, various post-Renaissance positivist, liberal, realist or critical theories, and, on the other hand, the classical natural law or justice theories of antiquity or the middle ages, including such figures as Aristotle, Cicero, Augustine or Aquinas. Many theorists, however, while acknowledging superficial differences among the various classical theories, fail to appreciate the variety and complexity of pre-modern thought. Unduly simplifying pre-modern understandings of law, they end up drawing false distinctions between modern and pre-modern legal theory. The pre-modern example considered in this article is Plato. Unlike scholars within the Humanities, who have continued to revise their approaches to pre-modern thought (often reflecting changes in ethical or political thought today), legal theorists, including many who claim to challenge much of traditional positivism, have scarcely moved beyond traditional positivists’ ahistorical and reductionist views.