Professor Block's book is among the most famous of the great defenses of victimless crimes and controversial economic practices, from profiteering and gouging to bribery and blackmail. However, beneath the surface, this book is also an outstanding work of microeconomic theory that explains the workings of economic forces in everyday events and affairs.

Murray Rothbard explains why: "Defending the Undefendable performs the service of highlighting, in the fullest and starkest terms, the essential nature of the productive services performed by all people in the free market. By taking the most extreme examples and showing how the Smithian principles work even in these cases, the book does far more to demonstrate the workability and morality of the free market than a dozen sober tomes on more respectable industries and activities. By testing and proving the extreme cases, he all the more illustrates and vindicates the theory.

"F.A. Hayek agreed, writing the author as follows: "Looking through Defending the Undefendable made me feel that I was once more exposed to the shock therapy by which, more than fifty years ago, the late Ludwig von Mises converted me to a consistent free market position. Even now I am occasionally at first incredulous and feel that 'this is going too far,' but usually find in the end that you are right. Some may find it too strong a medicine, but it will still do them good even if they hate it. A real understanding of economics demands that one disabuses oneself of many dear prejudices and illusions. Popular fallacies in economics frequently express themselves in unfounded prejudices against other occupations, and in showing the falsity of these stereotypes you are doing a real service, although you will not make yourself more popular with the majority."