In 1900 he began a professional career at the Public Library of Victoria and also enrolled at the University of Melbourne, graduating B.A. in 1905 and M.A. with first-class honours in philosophy in 1907. The achievement of Federation deepened his political interests and nationalist enthusiasm, while, under the influence of Professor Henry Laurie, he developed an abiding passion for Kant and idealism.

In 1908 Miller travelled, notably in Scotland and Germany. He visited Rudolph Eucken, whose ethical idealism came close to his own world-view, and on Deakin’s introduction met
L. S. Amery and other proponents of Imperial federation. On his return to Melbourne he published several pamphlets in this cause as well as his first Kantian essay—an attempt to develop a synthesis of Kant and modern relativists (particularly William James) and so provide an ethical basis for active citizenship.

Miller was hoping for an academic career. Further research in Melbourne’s philosophy department resulted in Kant’s Doctrine of Freedom (1913) and in April 1913 he became Lecturer in Philosophy and Economics at the University of Tasmania.