They did, for centuries, work a distinct and palpable deliverance on the
earth; while all the solemn and earnest meditation of the Neoplatonists,
however good or true, worked no deliverance whatsoever. Plotinus longed
at one time to make a practical attempt. He asked the Emperor
Gallienus, his patron, to rebuild for him a city in Campania; to allow
him to call it Platonopolis, and put it into the hands of him and his
disciples, that they might there realise Plato's ideal republic.
Luckily for the reputation of Neoplatonism, the scheme was swamped by
the courtiers of Gallienus, and the earth was saved the sad and
ludicrous sight of a realised Laputa; probably a very quarrelsome one.
That was his highest practical conception: the foundation of a new
society: not the regeneration of society as it existed.

That work was left for the Christian schools; and up to a certain point
they performed it. They made men good. This was the test, which of the
schools was in the right: this was the test, which of the two had hold
of the eternal roots of metaphysic. Cicero says, that he had learnt
more philosophy from the Laws of the Twelve Tables than from all the
Greeks. Clement and his school might have said the same of the Hebrew
Ten Commandments and Jewish Law, which are so marvellously analogous to
the old Roman laws, founded, as they are, on the belief in a Supreme
Being, a Jupiter--literally a Heavenly Father--who is the source and the
sanction of law; of whose justice man's justice is the pattern; who is
the avenger of crimes against marriage, property, life; on whom depends
the sanctity of an oath. And so, to compare great things with small,
there was a truly practical human element here in the Christian
teaching; purely ethical and metaphysical, and yet palpable to the
simplest and lowest, which gave to it a regenerating force which the
highest efforts of Neoplatonism could never attain.