Step 1: Recall the two fundamental approaches in physics.
Physics progresses by explaining diverse observations through fewer fundamental laws.
Step 2: Define unification with historical examples.
Unification merges separate phenomena under one theory, e.g., Maxwell unifying electricity and magnetism into electromagnetism.
Step 3: Define reduction with an example.
Reduction derives macroscopic behavior from microscopic constituents, e.g., thermodynamics from statistical mechanics of molecules.
Step 4: Final Answer:
Unification and reduction.