Doctrines are established beliefs or principles that guide the practices and teachings of a particular group, often found in religious, political, or legal contexts. They serve as foundational ideas that help followers understand their values and make decisions. For example, the Doctrine of the Trinity in Christianity explains the nature of God as three persons in one essence. In addition to religion, doctrines can also be seen in political ideologies, such as the Monroe Doctrine, which shaped U.S. foreign policy in the 19th century. These principles provide a framework for understanding complex issues and can influence behavior and societal norms.