The theory of general relativity, as well as early developments in atomic physics, clearly tell us, Weyl (1921b) suggests, that matter uniquely determines the field, and that there exist deeper underlying physical laws with which modern physics, such as quantum theory, is concerned, which specify “how the field is affected by matter”. That is, experience tells us that matter plays the role of a causal agent which uniquely determines the field, and which therefore has an independent physica