<p><strong>Noun</strong></p><ul><li>A branch of philosophy that treats of first principles, includes ontology and cosmology, and is intimately connected with epistemology.</li><li>Philosophy, especially in its more abstruse branches.</li><li>The underlying theoretical principles of a subject or field of inquiry.</li><li>(Initial capital letter, italics) A treatise (4th century B.C.) by Aristotle, dealing with first principles, the relation of universals to particulars, and the teleological doctrine of causation.</li></ul>