A smoker ignores quit advice. Why might motivational interviewing succeed where scolding fails? It resolves ambivalence - exploring the patient's own reasons to quit (health, money, family) rather than imposing the dentist's; the 5 A's framework structures it. Students learn behaviour's law: information rarely changes behaviour, motivation does - so tobacco control pairs policy (taxation, bans) with chairside counselling that elicits the patient's own motives.