LVIII. (167) And this appears to me to be the reason why the sentence which I have cited above was uttered. Day is an emblem of light, and the light of the soul is instruction. Many persons therefore have provided for themselves the lights that can exist in the soul against night and darkness, but not against day-time and light; such lights for instance, as are derived from rudimental instruction, and those branches of education which are called encyclical, and philosophy itself, which is sought after for the sake both of the pleasure which is derived from it, and also of the influence which it gives among rulers. But the good man seeks the day for the sake of the day, and the light for the light's sake; and he labours to acquire what is good for the sake of the good itself, and not of anything else, on which account Moses adds, "In order that I may tempt them and see whether they will walk according to my law or Not,"[Ex 16:4.] for the divine law enjoins us to honour virtue for its own sake. (168) Accordingly, right reason tests those who practise virtue as one might test a coin, to see whether they have contracted any stain, referring the good things of the soul to any of the external things; or whether they decide upon it as good money, preserving it in the intellect alone. These men are nourished not on earthly things, but on heavenly knowledge.