All complex systems contain parasites. In any system of cooperative behavior, an uncooperative strategy will be effective — and the system will tolerate the uncooperatives — as long as they’re not too numerous or too effective. Thus, as a species evolves cooperative behavior, it also evolves a dishonest minority that takes advantage of the honest majority. If individuals within a species have the ability to switch strategies, the dishonest minority will never be reduced to zero. As a result, the species simultaneously evolves two things: 1) security systems to protect itself from this dishonest minority, and 2) deception systems to successfully be parasitic. Humans evolved along this path. The basic mechanism can be modeled simply. It is in our collective group interest for everyone to cooperate. It is in any given individual’s short-term self interest not to cooperate: to defect, in game theory terms. But if everyone defects, society falls apart. To ensure widespread cooperation and minimal defection, we collectively implement a variety of societal security systems. Two of these systems evolved in prehistory: morals and reputation. Two others evolved as our social groups became larger and more formal: laws and technical security systems. What these security systems do, effectively, is give individuals incentives to act in the group interest. But none of these systems, with the possible exception of some fanciful science-fiction technologies, can ever bring that dishonest minority down to zero.
— Bruce Schneier, in his forthcoming book, The Dishonest Minority: Security and its Role in Modern Society
