Philo's philosophical exposition of the Ten Commandments, explaining why they were given in the wilderness, split into two tablets of five, and why each of the ten is the summary heading for a whole class of specific laws.
The Decalogue is Philo of Alexandria's treatise on the Ten Commandments, part of his larger exposition of the Law of Moses. Philo opens by asking why Moses gave the laws in the wilderness rather than in a city, and answers with several reasons: cities breed vanity, corruption, and counterfeit values that would have distracted the people; the soul receiving sacred laws needs to be purified first, like a patient prepared before treatment; and giving the law far from any city helped convince people that it came from God rather than from a human legislator. He also explains why God addressed the assembled multitude as if speaking to a single person, and why the commandments were engraved on two tablets of five.
Philo then works through the Ten Commandments themselves, treating the first tablet as duties toward God -- the existence of one sovereign God, the prohibition of images and idols, the ban on misusing God's name, and the sanctity of the seventh day -- with the fifth commandment, honoring parents, placed deliberately at the hinge between the two tablets because parents stand between the divine and the human. The second tablet covers duties toward other people: against adultery, murder, theft, false witness, and covetous desire, each explained through its rational and social harms rather than merely asserted as forbidden. Along the way Philo digresses at length into number theory (why ten is a perfect number), critiques Egyptian animal worship and Greek mythological explanations of the cosmos, and uses natural examples like storks caring for aged parents to argue for filial duty.
The work matters as an early and sophisticated instance of a Hellenized Jewish thinker translating biblical law into the vocabulary of Greek philosophy and rhetoric -- treating the commandments not as arbitrary decrees but as rationally grounded 'summary headings' (kephalaia) under which Philo says the Bible's more detailed particular laws are all classified. It shows how a first-century Alexandrian intellectual argued for the coherence and universality of Mosaic law to an audience shaped by Greco-Roman ethics and cosmology.
“Let us, then, engrave upon ourselves as the first commandment, and the most sacred of commandments, to believe in and honor the one supreme God; and let the doctrine of many gods not so much as touch the ears of a man accustomed to seek truth purely and without guile.”
— The Decalogue · read this chapter →
“The fourth commandment concerns the sacred seventh day, that it be observed with reverence and holiness. Some cities celebrate this once a month, reckoning from the new moon according to God's ordinance, but the nation of the Jews observes it continually, every six days without interruption.”
— The Decalogue · read this chapter →
“Since unlawful union produces such calamities, adultery — a thing rightly loathed and hated by God — was fittingly recorded as the first of the offenses.”
— The Decalogue · read this chapter →
“The second commandment is not to murder. For nature, having brought forth the most gentle of animals, man, as a creature suited to flock and community, called him to concord and fellowship, giving him reason as a means to bind together harmony and blending of characters.”
— The Decalogue · read this chapter →
“Among storks, the aged ones remain in their nests, unable to fly, while their offspring, flying over what I might almost call the whole earth and sea, bring in food for their parents from every quarter.”
— The Decalogue · read this chapter →
It is Philo of Alexandria's philosophical commentary on the Ten Commandments, explaining why Moses gave the law in the wilderness, why it was split across two tablets, and giving a rational justification for each of the ten commandments in turn.
He gives several reasons: cities are full of vanity and corrupt values that would distract the people, the soul needed purifying before receiving sacred law like a patient before treatment, and the remote setting helped convince people the law came from God rather than a human lawgiver.
He treats them as two tablets of five: the first tablet covers duties to God (one sovereign God, no images, proper use of God's name, the Sabbath, and honoring parents), and the second covers duties to other people (adultery, murder, theft, false witness, and desire).
Philo says the commandment to honor parents sits at the border between the two tablets because parents partake of both mortal and divine nature -- mortal in body, but godlike in the act of begetting -- so it closes the divine set and opens the human set.
He argues that worshiping soulless carved images is worse than worshiping the sun or heavens, since it degrades the worshiper: he says those who pray to lifeless idols effectively pray to become as blind, deaf, and inert as the images themselves.
He explains each one rationally -- for example arguing that adultery corrupts lineage and destroys households, and that false witness corrupts truth itself -- treating them as reasoned conclusions rather than arbitrary decrees, and calling each commandment a summary heading for many specific biblical laws.
Allegorical Interpretation I · Allegorical Interpretation II · Allegorical Interpretation III · Every Good Man is Free · Flaccus · On Abraham · On Dreams · On Drunkenness · On Flight and Finding · On Husbandry · On Joseph · On Mating / Preliminary Studies