Metaphysics is primarily concerned with understanding the fundamental nature of reality, including the existence and properties of objects, events, and abstract entities.

Aristotle is generally credited with introducing the term "metaphysics" in his work titled "Metaphysics", which explored the nature of being and the first principles of reality.

The ontological argument, most notably proposed by Anselm of Canterbury, asserts that the existence of God is a necessary truth that can be deduced from the concept of God as a being that is perfect in every way.

The problem of universals examines the relationship between general concepts (universals), such as "redness" or "humanity", and individual objects that possess those properties.

In metaphysics, substance refers to the fundamental and enduring essence of an object that underlies its changing properties and qualities.

Leibniz is associated with the theory of monism, which posits that there is only one fundamental substance or reality underlying all things in the universe.

Free will in metaphysics explores the idea that individuals possess the capacity to make choices and act according to their own volition, independent of external constraints or predetermined outcomes.

The problem of induction in metaphysics raises concerns about the reliability of inductive reasoning, which involves making general statements based on observed patterns, in establishing universal truths or metaphysical principles.

Kant is renowned for his theory of transcendental idealism, which posits that the structure and content of human knowledge are shaped by the innate categories and principles of the mind, rather than being derived solely from external reality.

Qualia, in metaphysics, refer to the subjective, conscious experiences of sensory qualities, such as the taste of sweetness, the color of red, or the feeling of pain.

Plato's concept of the "divided line" is a metaphor used to illustrate the different levels of reality and knowledge, ranging from the realm of shadows and illusions to the realm of pure Forms or Ideas.

Emergence in metaphysics explores the idea that certain properties and behaviors can arise from the interactions of simpler components in complex systems, giving rise to new phenomena that cannot be fully explained by the properties of the individual components.

Descartes is known for his theory of substance dualism, which posits that there are two fundamentally distinct substances: mind and matter, each with its own unique properties and attributes.

Causation in metaphysics examines the relationship between events or states of affairs in which one event (the cause) brings about another event (the effect), exploring the nature and mechanisms of causal connections.

Kant is known for his concept of the "categorical imperative", which refers to a moral principle that guides actions based on reason and universalizability, rather than personal desires or consequences.