Doctrine is a set of beliefs, principles, or rules that guide the behavior of a group or individual. An INSTRUCTION is an order or direction given to someone to do something, while a PRINCIPLE is a FUNDAMENTAL truth or LAW that serves as the basis for a system of BELIEF or behavior. A REGULATION is a RULE or directive made and maintained by an authority. A POSTULATE is a statement accepted as true without proof, while an OPINION is a view or judgement formed about something, not necessarily based on fact or knowledge. PHILOSOPHY is the study of the FUNDAMENTAL nature of knowledge, reality, and existence. A CONVICTION is a strong BELIEF or OPINION, while DOXY is a set of beliefs or opinions. A RULE is an official INSTRUCTION or REGULATION, while an IDEA is a thought or suggestion as to a possible course of action. LAW is a system of rules that are enforced through social institutions to govern behavior. FUNDAMENTAL is serving as an original or generating source, while a BELIEF is an acceptance that something exists or is true, especially one without proof. LORE is a body of traditions and knowledge on a subject or held by a particular group, while a CANON is a set of principles or rules. GOSPEL is a set of teachings or beliefs that are accepted as true, while an ISM is a distinctive practice, system, or PHILOSOPHY. CREDO is a statement of the beliefs or aims that guide someone's actions, while a creed is a set of beliefs or aims that guide someone's actions. DOGMA is a PRINCIPLE or set of principles laid down by an authority as incontrovertibly true, while a TENET is a PRINCIPLE or BELIEF, especially one of the main principles of a religion or PHILOSOPHY. Truman is a doctrine of international relations formulated by US President Harry S. Truman in 1947, while a PRECEPT is a RULE intended to regulate behavior or thought. Ideology is a system of ideas and ideals, especially one which forms the basis of economic or political theory and policy.