Causation is a major topic in metaphysics concerned with the relationship between causes and their effects. Philosophical inquiry into causation asks what it means for one event to bring about another, whether causal relationships are necessary or merely observed patterns, and how causation relates to change, time, determinism, agency, and natural law. Different theories have treated causation as a real connection between events, a regular sequence of occurrences, or a framework through which relationships in reality are interpreted.