Undine (Ondine)

In Paracelsus's elemental taxonomy the undine is the water-associated member of a class of elemental spirit-people who are the invisible, spiritual counterparts of visible nature. The term (undine/ondine) derives from Latin unda ('wave') with a diminutive -ina and first appears in Paracelsus's Book on Nymphs (published posthumously 1566). Later Romantic and 19th-century literature (notably Friedrich de la Motte Fouqué's novella Undine) expanded Paracelsus's technical category into a narrative figure whose marriage to a human is the mechanism by which she can obtain an immortal human soul.

Paracelsian and encyclopedic sources emphasize that undines resemble human beings in shape and are almost invariably depicted as female. Later literary treatments elaborate their water-nymph likeness and portray them as beautiful; specific morphological features vary across adaptations, but the core depiction in the cited sources is a humanoid, feminine water spirit often associated with springs, pools, and waterfalls.

As elemental inhabitants of water, undines occupy an unseen, parallel layer of being tied to the element of water and are associated with watery places of landscape. Paracelsus's account describes them as able to consort with humans—uniquely among the elemental spirits, a female undine may marry a human male. Paracelsus states undines lack an immortal human soul by default; marriage with a human confers an immortal soul on the undine and grants human souls to offspring. Literary developments add motifs in which marital promises, fidelity, or insults (especially in the presence of water) have metaphysical consequences, including the undine returning to her element with harmful results for the human partner.