1. Perfect competition (the benchmark): many sellers, no single firm's power — price equals cost.
2. Monopoly's harms: output restricted, price raised, innovation dulled — the deadweight triangle.
3. Harvard school (structure-conduct-performance): concentration breeds abuse — break up bigness; the mid-century orthodoxy.
4. Chicago school: efficiency first — most "abuse" is competition; consumer-welfare standard narrows the inquiry; the 1980s+ orthodoxy (Bork's Antitrust Paradox — in the course references — its manifesto).
5. Post-Chicago / neo-Brandeisian: strategic exclusion is real; platforms changed the game — the current revival (the Big-Tech cases of Unit 7's trends).