[From English essential, having real existence or related to the intrinsic nature of a thing; derived from Latin essentia: being.]
(metaphysics) The view that concepts have real existence; another term for Platonic idealism.
(epistemology) The view that all entities have intrinsic properties that can be discerned by reason (sometimes attributed to Aristotelianism but more akin to Platonism and neo-Platonism).