Are you confused about the Holy Trinity?- Modalism

I recently read an expression by a professing reformed Christian that led me to wonder if he is a modalist.

This article by Matt Slick is a brief discussion of this heresy.

Modalism is probably the most common theological error concerning the nature of God.  It is a denial of the Trinity. Modalism states that God is a single person who, throughout biblical history, has revealed Himself in three modes, or forms.  Thus, God is a single person who first manifested himself in the mode of the Father in Old Testament times.  At the incarnation, the mode was the Son and after Jesus‘ ascension, the mode is the Holy Spirit.  These modes are consecutive and never simultaneous.  In other words, this view states that the Father, the Son, and the Holy Spirit never all exist at the same time, only one after another.  Modalism denies the distinctiveness of the three persons in the Trinity even though it retains the divinity of Christ.

Present day groups that hold to forms of this error are the United Pentecostal and United Apostolic Churches.  They deny the Trinity, teach that the name of God is Jesus, and require baptism for salvation.  These modalist churches often accuse Trinitarians of teaching three gods.  This is not what the Trinity is.  The correct teaching of the Trinity is one God in three eternal coexistent persons:  The Father, the Son, and the Holy Spirit.

Westminster Larger Catechism

Q. 8. Are there more Gods than one? A. There is but one only, the living and true God.

Q. 9. How many persons are there in the Godhead? A. There be three persons in the Godhead, the Father, the Son, and the Holy Ghost; and these three are one true, eternal God, the same in substance, equal in power and glory; although distinguished by their personal properties.

Q. 10. What are the personal properties of the three persons in the Godhead? A. It is proper to the Father to beget the Son, and to the Son to be begotten of the Father, and to the Holy Ghost to proceed from the Father and the Son from all eternity.

Q. 11. How doth it appear that the Son and the Holy Ghost are God equal with the Father? A. The Scriptures manifest that the Son and the Holy Ghost are God equal with the Father, ascribing unto them such names, attributes, works, and worship, as are proper to God only.

 

Chalcedonian Creed (451 A.D.)

This creed was adopted at the Fourth Ecumenical Council, held at Chalcedon, located in what is now Turkey, in 451, as a response to certain heretical views concerning the nature of Christ.  It established the orthodox view that Christ has two natures (human and divine) that are unified in one person.
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We, then, following the holy Fathers, all with one consent, teach men to confess one and the same Son, our Lord Jesus Christ, the same perfect in Godhead and also perfect in manhood; truly God and truly man, of a reasonable [rational] soul and body; consubstantial [co-essential] with the Father according to the Godhead, and consubstantial with us according to the Manhood; in all things like unto us, without sin; begotten before all ages of the Father according to the Godhead, and in these latter days, for us and for our salvation, born of the Virgin Mary, the Mother of God, according to the Manhood; one and the same Christ, Son, Lord, only begotten, to be acknowledged in two natures, inconfusedly, unchangeably, indivisibly, inseparably; the distinction of natures being by no means taken away by the union, but rather the property of each nature being preserved, and concurring in one Person and one Subsistence, not parted or divided into two persons, but one and the same Son, and only begotten, God the Word, the Lord Jesus Christ; as the prophets from the beginning [have declared] concerning Him, and the Lord Jesus Christ Himself has taught us, and the Creed of the holy Fathers has handed down to us.