Unlike most of his contemporaries in Britain, Müller had what would be seen today as a normal scientific education at the universities of Berlin and Greifswald, culminating in a doctoral degree. Then, he decided to study medicine. As a medical student, he began to question religion and in 1846 became an atheist. Despite completing the course, he did not graduate because he refused to swear the graduation oath, which contained the phrase "so help me God and his sacred Gospel".