Modern apologists for Judaism have been found who, trying to force science to support their tottering faith, allege that the dietary law is hygienic.  Philo relies on no such treacherous reed.  We may not eat, he says,[165] the flesh of the pig or shell-fish, not because they are unhealthy, but because they are the sweetest and most delightful of all food, and for that very reason they are marks of the sensual life.  This and this alone is the true religious justification of the dietary law.

In this way, by showing how the letter represents the spirit, Philo fulfils the law; his religion is liberal in thought, conservative in practice.  He sees clearly that to throw off the law and reject tradition involves in the end chaos and the overthrow of righteousness.  And certain Christian—­and other—­theologians, if one may make bold to say so, fail to realize the spirit of Philo, when they speak of him as a man who approached the light, but was too tied down by the old traditions to receive the full illumination.  Rather is it true that the Jewish aspiration of “freedom under the law,” or spirit through the letter, is absolutely fundamental in Philo, and loyalty to the Torah is a guiding principle in his religious outlook.  He asserts it clearly and strikingly, not only in his ethical commentary on the law, but in his philosophical allegories.  Both passages deserve quotation, since they mark the fundamental contrast between Philo and non-Jewish allegorists of the law.  In the first Philo is commenting upon the command “Thou shalt not add to or take away from the law” (Deut. xix. 14).[166] He shows first how each of the virtues is marred by excess in either direction; virtue in fact, according to the Aristotelian formula, is “a mean.”

“And in the same way, if we add anything great or small to piety, the queen of virtues, or take anything away, we mar it and change its form.  Addition will engender superstition, and diminution impiety, and true piety will disappear, which above all things we should pray for to enlighten our souls:  for it is the cause of the greatest of goods, inducing in us a knowledge of our conduct towards God, which is a thing more royal and kingly than any public office or distinction.  Further, Moses lays down another general command, ’Do not remove the boundary stone of thy neighbor, which thy ancestors have set up.’  This, methinks, does not refer merely to inheritances and the boundary of land, but it is ordained with a view to the preservation of ancient customs.  For customs are unwritten laws, the decrees of men of old, not carved indeed upon pillars and inscribed upon parchment, but engraved upon the souls of the generations who through the ages maintain the chosen community.  Children should take over the paternal customs from their parents as part of their inheritance, for they were reared on them, and lived on them from their swaddling days, and they should not neglect them merely because the tradition is not written.  The man who obeys the written laws is not, indeed, worthy of praise, for he may be constrained thereto by fear of punishment.  But he who holds fast to the unwritten laws gives proof of a voluntary goodness and is worthy of our eulogy.”

Clearly he is arguing here for the observance of the oral law, which later was standardized in the Halakah.