The most important justification for strict legal and social controls on drugs is dependency or addiction. This is the kind of drug use that produces the most serious effects on health, productivity, and family life. Even more important, it provides the best reason for saying that the drug user is not free, and that anyone exposed to the drug may lose personal freedom. Respecting a person's freedom may not require respecting his or her desires if those desires are addictive or may produce a dependency. Besides, addiction and dependence are what make us think of drug abusers as sick and drug use as primarily a medical problem rather than a mere taste or pursuit. Dependency makes the drug user resemble a child or a patient, who can justifiably be deprived of autonomy.

But human lives are inconceivable without habitual actions; virtues and vices are habits; our personalities, and the very continuity of our selves, are partly constituted from habits, in the sense of learned dispositions to certain ways of responding and behaving. There is no sharp line between acts determined by choice and those determined by habit.