Holy Spirit, also called Paraclete, or Holy Ghost, (from Old English gast, “spirit”), in Christian belief, the third person of the Trinity. Numerous outpourings of the Spirit are mentioned in the Acts of the Apostles, in which healing, prophecy, the expelling of demons (exorcism), and speaking in tongues (glossolalia) are particularly associated with the activity of the Spirit.
Christian writers have seen in various references to the Spirit of Yahweh in the Hebrew Scriptures an anticipation of the doctrine of the Holy Spirit. The Hebrew word ruaḥ (usually translated “spirit”) is often found in texts referring to the free and unhindered activity of God, either in creating or in revitalizing creation, especially in connection with the prophetic word or messianic expectation. There was, however, no explicit belief in a separate divine person in biblical Judaism; in fact, the New Testament itself is not entirely clear in this regard. One suggestion of such belief is the promise of another helper, or intercessor (paraclete), that is found in the Gospel According to John.
The definition that the Holy Spirit was a distinct divine Person equal in substance to the Father and the Son and not subordinate to them came at the Council of Constantinople in ad 381, following challenges to its divinity. The Eastern and Western churches have since viewed the Holy Spirit as the bond, the fellowship, or the mutual charity between Father and Son; they are absolutely united in the Spirit. The relationship of the Holy Spirit to the other Persons of the Trinity has been described in the West as proceeding from both the Father and the Son, whereas in the East it has been held that the procession is from the Father through the Son.
Most Catholic and Orthodox Christians have experienced the Holy Spirit more in the sacramental life of the church than in the context of such speculation. From apostolic times, the formula for Baptism has been Trinitarian. Confirmation (in the Eastern Orthodox Church, chrismation) although not accepted by Protestants as a sacrament, has been closely allied with the role of the Holy Spirit in the church. The Eastern Orthodox Church has stressed the role of the descent of the Spirit upon the worshipping congregation and upon the eucharistic bread and wine in the prayer known as the epiclesis.
From the earliest centuries of the Christian church, various groups, discontented with the lack of freedom, active charity, or vitality in the institutional church, have called for a greater sensitivity to the ongoing outpourings of the Holy Spirit; among such movements were the Holiness and Pentecostal movements of the 19th and 20th centuries. Being “filled” with the Holy Spirit is seen as the corollary of one’s salvation. See also Trinity.