cornerstone

Cornerstone is Old English, a compound of corner (from Latin cornu, horn — the projecting angle) and stone. In masonry, the cornerstone is the first stone laid at the junction of two walls. It is set with precision because every subsequent measurement is taken from it. If the cornerstone is wrong, the building is wrong. The word names the stone upon which all other stones depend.

The metaphor is ancient and cross-cultural. The Hebrew Bible refers to the cornerstone in Psalm 118: 'The stone which the builders rejected has become the chief cornerstone.' Isaiah 28 describes a 'tested stone, a precious cornerstone, a sure foundation.' The Christian New Testament applies these passages to Christ. The metaphor of the cornerstone — the foundation that determines everything built upon it — is among the oldest in Western literature.

Ceremonial cornerstone-laying became a formal practice in the eighteenth century. George Washington laid the cornerstone of the U.S. Capitol on September 18, 1793, in a Masonic ceremony. The practice of placing documents, coins, and newspapers inside cornerstones — time capsules embedded in the foundation — made the cornerstone a ritual object as well as a structural one. The building records its own origin in its most foundational stone.

Modern construction does not technically require cornerstones. Steel-frame and reinforced concrete buildings are not built by stacking stones from a corner. But the ceremonial cornerstone persists — political leaders still lay them for hospitals, libraries, and government buildings. The word has become entirely figurative in most contexts: 'the cornerstone of the argument,' 'the cornerstone of her career,' 'the cornerstone of the policy.' The stone is metaphorical. The function — the thing everything else depends on — is literal.