Sensationalistic Phenomenalism and Economy of Thought. On Ernst Mach's Concept of Science. Ernst Mach, natural scientist and major precursor of the Vienna Circle, never wants to be a philosopher. Nevertheless his writings are full of valuable hints for a modern theory of human knowledge – with respect to economical, historical and evolutionary aspects. His kind of phenomenalism is sensationalistic, monistic and instrumentalistic. This article deals with some contributions of his approach to actual debates in the general philosophy of science.