Hypostasis (philosophy and religion)
Hypostasis (Greek: ὑπόστασις, "hypóstasis") is the underlying state or underlying substance and is the fundamental reality that supports all else. In Neoplatonism the hypostasis of the soul, the intellect ("nous") and "the one" was addressed by Plotinus. In Christian theology, the Holy Trinity consists of three "hypostases": Hypostasis of the Father, Hypostasis of the Son, and Hypostasis of the Holy Spirit. Ancient Greek philosophy. Pseudo-Aristotle used "hypostasis" in the sense of material substance. Neoplatonists argue that beneath the surface phenomena that present themselves to our senses are three higher spiritual principles, or hypostases, each one  more sublime than the preceding. For Plotinus, these are the Soul, the Intellect, and the One. Christian theology. The term hypostasis has a particular significance in Christian theology, particularly in Christian Triadology (study of the Holy Trinity), and also in Christology (study of Christ). Hypostasis in Christian Triadology. In Christian Triadology (study of the Holy Trinity) three specific theological concepts have emerged throughout history, in reference to number and mutual relations of divine hypostases: Hypostasis in Christology. Within Christology, two specific theological concepts have emerged throughout history, in reference to the Hypostasis of Christ: History of use. In early Christian  writings, hypostasis was used to denote "being" or "substantive reality" and was not always distinguished in meaning from terms like "ousia" ('essence'), substantia ('substance') or qnoma (specific term in Syriac Christianity). It was used in this way by Tatian and Origen and also in the anathemas appended to the Nicene Creed of 325. It was mainly under the influence of the Cappadocian Fathers that the terminology was clarified and standardized so that the formula "three hypostases in one ousia" came to be accepted as an epitome of the orthodox doctrine of the Trinity. The first person to propose a difference  in the meanings of hypostasis and ousía, and for using hypostasis as synonym of Person, was Basil of Caesarea, namely in his letters 214 (375 A.D.) and 236 (376 A.D.) Specifically, Basil of Caesarea argues that the two terms are not synonymous and that they, therefore, are not to be used indiscriminately in referring to the Godhead. He writes: This consensus, however, was not achieved without some confusion at first in the minds of Western theologians since in the West the vocabulary was different. Many Latin-speaking theologians understood "hypo-stasis" as "sub-stantia" (substance); thus when speaking of three  hypostases in the Godhead, they might suspect three "substances" or tritheism. However, from the middle of the fifth century onwards, marked by Council of Chalcedon, the word came to be contrasted with "ousia" and used to mean "individual reality," especially in the trinitarian and Christological contexts. The Christian concept of the Trinity is often described as being one God existing in three distinct "hypostases/personae/persons".