Metaphysics is the branch of philosophy that examines the basic structure of reality. It is often characterized as first philosophy, implying that it is more fundamental than other forms of philosophical inquiry. Metaphysics is traditionally seen as the study of mind-independent features of the world, but some modern theorists understand it as an inquiry into the conceptual schemes that underlie human thought and experience.

Many general and abstract topics belong to the subject of metaphysics. It investigates the nature of existence, the features all entities have in common, and their division into categories of being. An influential contrast is between particulars, which are individual unique entities, like a specific apple, and universals, which are general repeatable entities that characterize particulars, like the color red. Modal metaphysics examines what it means for something to be possible or necessary. The nature of space, time, and change is also discussed by metaphysicians. A closely related issue concerns the essence of causality and its relation to the laws of nature. Other topics include how mind and matter are related, whether everything in the world is predetermined, and whether there is free will.

• Space
• Time
• Modal metaphysics
• Theory of categories
• Determinism
• indeterminism
  • chance , probability
• Free will