 A different notion of reduction derives from the attempts of philosophers of science to explain intertheoretic reduction. The classic formulation of this notion was given by Ernest Nagel (1961). Nagel said that one theory was reduced to another if you could logically derive the first from the second together with what he called bridge laws, i.e., laws connecting the predicates of the reduced theory (the theory to be reduced) with the predicates of the reducing theory (the theory to which one is reducing). Here is a formulation of this idea, where the theories in question are psychology and neuroscience: