Every new theory encounters opposition and rejection at first. The adherents of the old, accepted doctrine object to the new theory, refuse it recognition, and declare it to be mistaken. Years, even decades, must pass before it succeeds in supplanting the old one. A new generation must grow up before its victory is decisive.

Let us consider first the doctrine which teaches that thought is dependent upon the class of the thinker.

In his De officiisCicero prescribed a code of social respectability and propriety that faithfully reflects the conceptions of gentility and merit that have prevailed in western civilization through the centuries. Cicero presented nothing new in this work, nor did he intend to. He availed himself of older, Greek standards. And the views that he expounded corresponded completely to those that had been generally accepted for centuries both in the Greek and Hellenistic world and in republican Rome.

The ultimate statement that the theory of knowledge can make without leaving the solid ground of science and engaging in vague speculations on fruitless metaphysical concepts is: Changes in what is given, as far as our experience is concerned, take place in a way that allows us to perceive in the course of things the rule of universal laws that permit of no exception.

Böhm-Bawerk expresses the opinion that the treatment of the theory of price determination should be divided into two parts.

The much talked about homo economicus of the classical theory is the personification of the principles of the businessman. The businessman wants to conduct every business with the highest possible profit: he wants to buy as cheaply as possible and sell as dearly as possible. By means of diligence and attention to business he strives to eliminate all sources of error so that the results of his action are not prejudiced by ignorance, neglectfulness, mistakes, and the like.