‘What is metaphysics?’ attempts to explain the discipline as trying to understand the fundamental nature of reality. Metaphysics seeks to organize and systematize all these specific truths that science discovers and to describe their general features. It thinks about the features that rationally the world should or could have. Science is based on observation and theories can be tested and disproved, whereas metaphysicists reject theories on the basis of reasoning alone. Metaphysical understanding of what the world is, how it works, and how it all fits together, in general and abstract terms, could be the most real and important thing there is.