Why are the Ten Commandments on two tablets?

The Torah records the Ten Commandments twice, in Exodus 20 and again in Deuteronomy 5, and both times specifies they were given on two stone tablets rather than one continuous list. Jewish tradition's most common explanation divides the ten by subject: the first tablet holds commandments 1 through 4 or 5, addressing a person's relationship to God — no other gods, no idols, not taking God's name in vain, keeping Shabbat, and (in one common grouping) honoring parents — while the second tablet holds the remaining commandments governing relationships between people: no murder, no adultery, no stealing, no false testimony, no coveting. Honoring parents sits at the hinge point in most versions of this division precisely because it bridges the two categories — parents stand in a God-like role of authority and origin toward a child, so the command to honor them belongs logically with duties toward God even though parents are, plainly, people. This bein adam laMakom (between a person and God) versus bein adam lachaveiro (between a person and another person) framework recurs throughout later rabbinic thought as a basic organizing principle for all of Jewish law, not just the Decalogue: some commandments repair a person's standing before God, others repair a person's standing with other people, and the two categories require different remedies when violated — repentance and prayer for the first, but restitution and reconciliation with the wronged party for the second. Reading the tablets as a matched pair rather than one long list makes a structural claim: right relationship with God and right conduct toward other people are treated as two halves of a single covenant, neither substituting for the other.