The classic catalogues (David, Zweigert & Kötz):
1. Cognitive/scientific: knowledge of law's varieties — a "laboratory" (Ihering's image) where institutions are tested across systems;
2. Pragmatic-legislative: the reformer's model-search (the drafting history of the German BGB, Japan's Meiji codes, the 2074 Codes — all comparative projects);
3. Interpretive: foreign law as persuasive authority (the "living instrument" readings; the courts' comparative constitutionalism);
4. Harmonizing/unificatory: the treaties' and model laws' foundation (CISG, UNIDROIT Principles, the EU's acquis; the East African and OHADA harmonizations);
5. Functional-operational: the practicing lawyer's foreign-law need (contracts, conflicts, cross- border litigation);
6. Critical/ideological: comparison as critique — exposing one's system's deficiencies and hidden assumptions (the functionalists' "praesumptio similitudinis" — the presumption that systems reach similar results — and its critics).