AVENARIUS, RICHARD HEINRICH LUDWIG German philosopher, was born in Paris and died at Zurich, where he had been professor of philosophy for nearly 20 years. At Leipzig he was one of the founders of the Akademisch philosophische Verein, and was the first editor of the Viertel jahrsschri f t fur wissenscha f tliche Philoso phie. His chief works are Philosophie als Denken der Welt gemass dean Princip des kleinsten Kraftmasses (1876) and the Kritik der reinen Erf ahr ung (1888-9o). In these works he made an attempt to co-ordi nate thought and action. Like Mach, he started from the prin ciple of economy of thinking, and in the Kritik endeavoured to explain pure experience in relation to knowledge and environ ment. He discovers that statements dependent upon environ ment constitute pure experience. This philosophy, called Empirio criticism, is not, however, a realistic, but an idealistic dualism, nor can it be called materialism.