Assessments:
Errol Harris
Constantin Brunner, who died in 1937, was a philosopher of considerable originality and importance to whom all too little attention has been paid until quite recently. (Foreword / by Errol E. Harris. In To live is to think, p. vii)

Devotees of Husserl and Existentialists of various types will be, perhaps, surprised to discover how far Brunner anticipated the major thinkers in the field of phenomenology. (Foreword / by Errol E. Harris. In To live is to think, p. viii)