In a recent article in Philosophy of Science P. C. Jones discusses the relation between idealism and science. He presents in a very clear way the essentials of the causal theory of perception—the theory which lies at the foundation of the scientific method of research, for the scientist who does not believe that we have a direct knowledge of the external world. He summarizes this causal theory as follows: “An incompletely conceived idealism pictures objects in space and time, and admits only that we have no direct knowledge of them—that what we know of them we merely infer from sensory impulses.”