What is defined as a set of ideas and beliefs that governs a system of thought?

The correct answer is ideology. Ideology refers to a comprehensive set of ideas and beliefs that form the foundation for understanding and interpreting social, political, and economic systems. It shapes the values and principles that guide a particular group or society in its worldview and decision-making processes.

Philosophy, while closely related, primarily focuses on the fundamental nature of knowledge, reality, and existence. It encompasses broader and often abstract inquiries rather than a specific system governing thoughts related to practical matters.

Methodology pertains to the systematic, theoretical analysis of the methods applied in a field of study. It outlines the specific procedures or techniques used to gather and analyze data, rather than a governing set of beliefs.

Theory represents a set of principles on which a particular subject is based, often developed through research and observation. It provides frameworks for understanding phenomena but does not encompass the wider beliefs and values that regulate thought processes in society.

In summary, ideology is the most fitting choice because it encapsulates the structured set of beliefs and ideas that drive systems of thought in a societal context, while the other terms have more specific or narrower meanings.