Adams point here (and Adam Smith's point) is that the simple pursuit of self interest in a free market leads one (like an invisible hand) to benefit others. Obviously, a free market system requires rule of law in order to prevent theft, fraud, etc. Could a grocer stay in business selling poison milk? Obviously not. As I recall the Chinese milk-adulterer was caught and sentenced to death. Attempts by speculators to corner the market have been failures because the rising prices create new entrants and encourage members of the cartel to make huge profits by "cheating" and undercutting their fellow cartel members.