Unlike the members of the physical and biological sciences, the economist is asked to explain his work in a manner that is interesting and convincing… - George Stigler

The user of a theory has a simpler task: his not to reason why, his but to sigh and try. If the right element in the diverse situations has been isolated, the theory will work: it will yield predictions better than those which can be reached with any alternative theory.

Consider the Negro as a neighbor. He is frequently repelled and avoided by the white man, but is it only color prejudice? On the contrary, it is because the Negro family is, on average, a loose, morally lax group, and brings with its presence a rapid rise in crime and vandalism. No statutes, no sermons, no demonstrations, will obtain for the Negro the liking and respect that sober virtues commend. And the leaders of Negro thought: they blame the crime and immorality upon the slums and the low income—as if individual responsibility could be bought with a thousand dollars a year.

Unexpected changes, on the contrary, lead to windfall gains or losses for those who are in the right or wrong places at a given time.