THE empirical sciences are systems of theories. The logic of scientific knowledge can therefore be described as a theory of theories.
Scientific theories are universal statements. Like all linguistic representations they are systems of signs or symbols. Thus I do not think it is helpful to express the difference between universal theories and singular statements by saying that the latter are 'concrete' whereas theories are merely symbolic formulae or symbolic schemata; for exactly the same may be said of even the most 'concrete' statements.*1
Theories are nets cast to catch what we call 'the world': to rationalize, to explain, and to master it. We endeavour to make the mesh ever finer and freer.
To give a causal explanation of an event means to deduce a statement which describes it, using as premises of the deduction one or more universal laws, together with certain singular statements, the initial conditions. For example, we can say that we have given a causal____________________