The iron law of prohibition also implies that if drugs are made legal, people will choose to use weaker and less dangerous forms. Hari shows that Oxycontin users make a rational decision when they switch to heroin, simply because of how the black market is structured. Needless to say, in a legal drug market, the government could give them the opposite incentive by making more
dangerous drugs more expensive. The doctor’s comments about relapse and growth are a metaphor for her (and Hari’s) hope that after repeating the drug war’s mistakes enough times, modern societies will eventually move past them.