A brief orientation
Solon is one of the few archaic-Greek figures who is securely historical, partly because fragments of his own poetry survive and partly because the institutional changes he introduced left a long political shadow. The Athenian tradition credits him with arriving at office around 594 BCE in a moment of severe crisis — agrarian debt, the prospect of mass enslavement of citizens for debt, the threat of civil war — and with using his year of extraordinary authority to write a new constitution that he then refused to remain to defend.
The Solonian reforms
The reforms are conventionally read as having two parts. The seisachtheia — the "shaking off of burdens" — cancelled outstanding debts and forbade enslavement for debt of any Athenian citizen, restoring those who had already been enslaved. The constitutional reforms reorganised political participation by property class rather than by birth, opened the magistracies to a broader range of citizens, and created a popular court (the heliaia) to which any citizen could appeal a magistrate's decision.
Solon refused to take the tyranny offered him and left the city for ten years to keep himself from being asked to amend his own laws. The settlement did not entirely hold — Peisistratus' tyranny followed within a generation — but the Solonian framework, including the principle that the people sit in judgement over magistrates, shaped what democratic Athens would later become.
Reception
Solon belongs to the canonical list of the Seven Sages and was read throughout antiquity as the type of the moderate lawgiver — neither revolutionary nor reactionary, willing to make hard compromises in the interest of holding the polity together. Plato's Timaeus opens with the famous Egyptian-priest conversation about him; Plutarch's Life is the long ancient treatment. The American founders, particularly through their reading of Plutarch, knew him by name.
Why he matters for Virtue & Power
Solon is the lawgiver who showed that a polity in crisis can be re-founded without a tyrant. The principle of his refusal to remain — that the laws have to stand on their own, not on the lawgiver's continued presence — is one of the platform's recurring lessons. See the theme on Founding.