At the age of thirteen, Einstein abandoned his religious fervor after studying the ideas of which 18th century philosopher suggested God might not exist? He is best known for metaphysics and ethics.

Albert Einstein was deeply influenced by Immanuel Kant's Critique of Pure Reason, which challenged traditional religious views and argued that knowledge comes from sensory experience shaped by mental structures. Kant's philosophical skepticism about metaphysical claims helped Einstein move away from religious faith. Ralph Emerson and Socrates were earlier philosophers; Nietzsche came later.