This document provides an overview of different classifications of law including natural law, positive law, sources of Philippine law, and how laws are classified under the Philippine legal system. It specifically discusses that the Law on Obligations and Contracts is substantive private civil law, meaning it establishes rights and duties between private individuals rather than dealing with public or political matters. A key principle discussed is the conclusive presumption of knowledge of the law as outlined in the Civil Code, which is that ignorance of the law is not an excuse for noncompliance.