After studying with Edmund Husserl in Göttingen and Carl Stumpf in Berlin, he habilitated in Munich in 1910.
He criticized Husserl's conception of evidence and intuition of essences.
Brunswig served in World War I and was awarded the Iron Cross, Second Class.
Through his experiences at the front, where he was "constantly looking death in the eye", he found the "courage for metaphysics" and emphasized Christian faith and German nationalism.
His interpretation of Leibniz in 1925 highlighted his role as a "Germanic thinker".