When we approach the study of business cycle with the intention of carrying through an analysis that is truly dynamic and determinate in the above se… - Ragnar Frisch

To proceed from assumptions about an abstract theoretical set-up and from them to draw conclusions about the observable world and to test - by rough or more refined means - whether the conformity with observations is "good" enough, is indeed the time honoured procedure that all empirical sciences, including the natural sciences, have used. I shall therefore not plead guilty of heresy even if I do work with choice-theory concepts that are not invariant under a general monotonic transformation of the utility indicator.

… in economic political discussions there is a nearly infinite number of specific questions that may be asked. Besides the ones mentioned in section 3 consider for instance these: "Should we build a road between points A and B in the country?", "Should we promote investments that will give employment to many people, or should we on the contrary promote such investment which will save labour?"… "Should we put more emphasis on things that have up to now not been included in the statistical concept of the gross national product? For instance, should we try to avoid air-pollution and all the kinds of intoxications that may be caused by refuse and waste (a problem that must be studied in its totality as a problem of circulation of matter in society, much in the same way as we study interindustry relations in an input-output table)?“, “Should we assess economic value to an undisturbed nature?” etc.

Deep in the human nature there is an almost irresistible tendency to concentrate physical and mental energy on attempts at solving problems that seem to be unsolvable.