Which core principle of the French Revolution most directly undermined the legal structure of the Ancien Régime’s Three Estates?

💡 Explanation:

The Ancien Régime was fundamentally defined by the legal privileges and exemptions of the First Estate (Clergy) and the Second Estate (Nobility) from the obligations, particularly taxation, borne by the Third Estate. The principle of 'Equality before the Law' directly challenged and eventually abolished this system of birth-based legal distinctions, establishing that all citizens were subject to the same laws and burdens, thus destroying the legal foundation of the Three Estates system.