Newtonian physics demonstrates the reality of science and so the possibility of a priori judgements.
But science progresses. It is never complete. Supplementing Kant's ethics with Aristotelian and biblical ideas of virtue and justice, Cohen championed universal human dignities and rebutted the anti-Semitic historian Treitschke, defending the loyalty of German Jews by appeal to the Kantian respect for moral subjects implicit in Jewish ethics. On his retirement, Marburg snubbed his chosen successor, Ernst Cassirer, and appointed Paul Natorp. God was the backstop of moral fairness and generosity, orientating human progress toward a community of free individuals.