This document discusses different schools of legal thought and their classification. It covers the natural law school, historical school, sociological school, positivist/analytical school, and realist school. For each school, it provides the main reasons for their emergence, key exponents, and their definition of law. The historical school focuses on law developing through customs. The sociological school sees law as a tool for social engineering. The positivist school treats law as commands from a sovereign. And the realist school defines law as what courts declare it to be.