  He believed that theories should be advanced to explain whatever data were available in a particular domain. These theories should preferably concern the underlying physical, causal mechanisms and ought, in any case, to go beyond the data which generated them. They are then tested by drawing out new predictions, which, if verified in experience, may confirm the theory and may eventually render it certain, at least in the sense that it becomes very difficult to deny. (Urbach 1987, 49) 