Natural law {Ans: It is defined as the divine inspiration in man of the sense of justice, fairness, and righteousness, not by divine revelation or formal promulgation, but by internal dictates of reason alone.}Obligation {Ans: Derived from the Latin word "obligatio" which means "tying" or "binding.". It is a juridical necessity to give, to do, or not to do. It is a tie or bond recognized by law by virtue of which one is bound in favor of another to render something and this may consist in giving a thing, doing a certain act, or not doing a certain act}Contractual Obligations {Ans: or obligations arising from contracts or voluntary agreements. A contract is a meeting of minds between two persons whereby one binds himself, with respect to the other, to give something or to render some service. (Art. 1305.) It is the formal expression by the parties of their rights and obligations they have agreed upon with respect to each other.}Judicial decisions or Jurisprudence {Ans: The decisions of the courts, particularly the Supreme Court, applying or interpreting the laws or the Constitution form part of the legal system of the Philippines. (Art. 8, Ibid.)}Divine law