But we must not deceive ourselves as to the humiliating truth that so far not the slightest effort has been made toward the answering of this central scientific question. If the inquiry into the psychical effects were really to be confined to this problem of the ultimate satisfaction of economic desires, scientific psychology could not contribute any results and could not offer anything but hopes and wishes for the future. At the first glance it might appear as if just here a large amount of literature exists; moreover, a literature rich in excellent investigations and ample empirical material. On the one side the political economists, with their theories of economic value and their investigations concerning the conditions of prices and the development of luxury, the calculation of economic values from pleasure and displeasure and many similar studies, have connected the economic processes with mental life; on the other side the philosophers, with their theories of value, have not confined themselves to the ethical and æsthetic motives, but have gone deeply into the economic life too. While such studies of the economists and of the philosophers are chiefly meant to serve theoretical understanding, it might seem easy to deduce from them technical practical prescriptions as well. If we know that under particular conditions certain demands will be satisfied, we draw the conclusion that we must realize those conditions whenever such demands are to be satisfied. The theoretical views of the economists and of the philosophers of value might thus be directly translated into psychotechnical advice.