(Greek: meta, after or beyond; physika, physics)
Historically this word probably originated with Andronicus of Rhodes who arranged the works of Aristotle in two series; the books on physics and those "after the physics."
This caption eventually was accepted as the title of the treatise immediately following it, because its subject matter is beyond the sense perceptible world.
In its traditional sense the term means the philosophical science which treats of the most fundamental principles underlying all reality such as being, its essential attributes, substance, cause.
Other sciences deal with special classes of beings: physics with physically mobile being; mathematics with quantified being; metaphysics abstracts from such determination of being, retaining only being itself.
It embraces therefore all beings whatsoever and considers them under the aspect of their beingness or entity.
Hence Aristotle defined it as the science of being as being.
In the Aristotelian and Scholastic conception it included ontology and natural theology.
Many modern philosophers extend its meaning, following Christian Wolff's division of general metaphysics, or ontology, and special metaphysics, comprising cosmology, rational psychology, and natural theology.
Bacon, on the contrary, limited its meaning to the study of final and formal causes, to distinguish it from physics, the science of material and efficient causes.
Descartes, basing metaphysics exclusively on mental phenomena, made it the science of the conditions of knowledge.
Many English philosophers practically identify it with psychology, or with epistemology.
Positivistic philosophy, which limits knowledge to the facts of sense experience, considers it an impossible science.
Kant, maintaining the inability of the pure or speculative reason to attain ultra physical reality in itself, restricts metaphysics to the role of defining the limits of human knowledge.
New Catholic Dictionary