Trump claims to be an expert—the world’s greatest—in anything and everything. As one video mash-up shows, Trump has at various times claimed—in all seriousness—that no one knows more than he does about: taxes, income, construction, campaign finance, drones, technology, infrastructure, work visas, the Islamic State, “things” generally, environmental-impact statements, Facebook, renewable energy, polls, courts, steelworkers, golf, banks, trade, nuclear weapons, tax law, lawsuits, currency devaluation, money, “the system,” debt, and politicians.