Elaborate legal enactments codified in Babylonia by the 10th century B.C. find striking parallels in Hebrew, late Jewish (Talmudic), Syrian and Mahommedan law, or in the unwritten usages of all ages; for even where there were neither written laws nor duly instituted lawgivers, there was no lawlessness, since custom and belief were, and still are, almost inflexible.
When Aristotle at the age of eighteen came to Athens, Plato, at the age of sixty-two, had probably written all his dialogues except the Laws; and in the course of the remaining twenty years of his life and teaching, he expounded " the socalled unwritten dogmas " in his lectures on the Good.
Legal rights are everywhere taking the place of unwritten customs. Land, which was before merely a source of livelihood to the cultivator and of revenue to the state, has now become the subject of commercial speculation.
The results are open to criticism in details, but form on the whole a remarkable achievement in the conversion of unwritten and highly technical law into a body of written law sufficiently clear to be administered by officers to many of whom its ideas and language are foreign.
There was therefore a written Platonism for Aristotle to read, and an unwritten Platonism which he actually heard.