Henri François d’Aguesseau (1668–1751) is a leadingexample of the justice and legal science of Ancien Régime France. His family origins and his education, his life as well as his career in the public prosecutor’s department of the parliament of Paris and later in the Chancellery of France explain his true influence and the model he quickly became for his generation and for later generations. But he is also a high moral figure of French Catholicism in the time of Louis XIV and Louis XV. Indeed, this was a particularly crucial period for Christian thought in France, at the dawn of the Enlightenment, at the time of the “crisis of the European conscience.” His views on the law, on the just and the unjust, on the evolution of the law, and on the exercise of justice and the administration of the judiciary cannot be understood, even in their apparent contradictions or hesitations, without understanding his prevailing preoccupation with the defense of religion in the political and social sphere as well as in the private sphere. He thus became one of the most representative personalities of a certain French conservatism, at once open to the lights of reason and irrevocably loyal to his faith.