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When Christianity arrived, it could not eliminate Brehon Law—too deeply rooted, too essential to social function. Instead, the Church adapted it.
Monks began writing down the laws (previously oral). Christian concepts were integrated—sin alongside crime, penance alongside compensation, church authority alongside traditional Brehons.
But the fundamental structure persisted. The honor-prices, the compensation system, the sureties—all continued, modified but recognizable. Brehon Law survived, in hybrid form, into the medieval period.
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