“The word ‘person’ has changed its meaning since the third century when it began to be used in connection with the ‘threefoldness of God’. When we talk about God as a person, we naturally think of God as being one person. But theologians such as Tertullian, writing in the third century, used the word ‘person’ with a different meaning. The word ‘person’ originally derives from the Latin word persona, meaning an actor’s face-mask—and, by extension, the role which he takes in a play. By stating that there were three persons but only one God, Tertullian was asserting that all three major roles in the great drama of human redemption are played by the one and the same God. The three great roles in this drama are all played by the same actor: God. Each of these roles may reveal God in a somewhat different way, but it is the same God in every case. So when we talk about God as one person, we mean one person in the modern sense of the word, and when we talk about God as three persons, we mean three persons in the ancient sense of the word. … Confusing these two senses of the word ‘person’ inevitably leads to the idea that God is actually a committee.”
Alister E. McGrath, Understanding the Trinity, pp 130-131
The heresy represented in this quote, unfortunately, is not uncommon. The Trinity as a whole is made out to be one person in the modern sense- that is, one rational individual being, one individual intelligent agent, one “He”; while the Father, Son, and Spirit are deemed to be nothing more than mere “masks” of this one individual. This is the same insidious heresy of Sabellius, only slightly modified. This is semi-modalism, and it is damnable heresy; this needs to be said, not to show malice to those who hold it, but to warn men of the danger it presents.
Semi-modalism equivocates on what “person” means, as this quote shows. A semi-modalist will insist that they are not a modalist because the Father, Son, and Spirit are “three persons”- yet when they use the word ‘person’, they mean something other than what is normally meant by ‘person’. They equivocate by using a non-standard definition of the term, usually without making that clear, like McGrath does above.
The Father, Son, and Holy Spirit are really three persons; not three modes, not three masks, of one and the self-same person, but are in fact and in truth three distinct rational individual beings. Scripture repeatedly teaches this: “Fall on us and hide us from the presence of Him who sits on the throne, and from the wrath of the Lamb; 17 for the great day of their wrath has come, and who is able to stand?” (Rev. 6:16-17 NASB) “Jesus answered and said to him, “If anyone loves Me, he will keep My word; and My Father will love him, and We will come to him and make Our home with him.” (John 14:23 NASB). The fact that scripture uses plural personal pronouns in these verses requires us to understand that the Father and Son are two persons.
“If I bear witness of Myself, My witness is not true. 32 There is another who bears witness of Me, and I know that the witness which He witnesses of Me is true… the Father Himself, who sent Me, has testified of Me. You have neither heard His voice at any time, nor seen His form.” John 5:31-32, 37 NKJV). The Son says here that He does not bear witness to Himself (v31). Yet He also says that the Father bears witness of Him- this require that He is a distinct person from His Father. The Father is not Him, but “another” Who can witness to Christ, without Christ witnessing to Himself. Were They the same person, the Father testifying to the Son would be the same as the Son testifying to Himself.
Semi-modalism is a dangerous heresy because making the Father, Son, and Spirit to be the masks or modes of one and the same person denies the central tenets of the Christian faith, by denying the real existence of the Son of the God, the one Mediator between God and man, apart from Whom no one can approach the Father.
“Now a mediator is not for one party only; whereas God is only one.” (Gal 3:20 NASB)
“For there is one God, and one mediator also between God and men, the man Christ Jesus,” (1 Tim 2:5 NASB)
It is clear that no person can be a mediator between themselves and another; the very nature of what a mediator between two parties is, requires that the mediator be a third party. If Christ then is the mediator between God and man, then He cannot be the same person, the same individual rational being, as the God to Whom He intercedes. If the Son is the same “person” as the Father according to the normal usage of the word, that is, the same rational individual being as the Father, then He cannot be a mediator between God and man, for this would make the mediator and the party being mediated to one and the same, which is impossible. As the Son would in fact be the same person as the Father Who we need a Mediator to approach, we would in fact have no Mediator- and so according to scripture, it would be impossible to approach God.
And so the God of the semi-modalists is unapproachable; for by making the Son and Spirit out to not really be distinct persons, but one and the same individual being as the Father, they deny their real existence. They have no one to Mediate between them and their God, and no one to sanctify them, since they have made the Mediator, the Son, and the Sanctifier, the Spirit, to be the very same one that they need a Mediator and a Sanctifier to approach.
And likewise, semi-modalism denies that saving confession, that Jesus Christ is the Son of God. For the Son of another is necessarily another person, Who relates to that other as a Son. But the semi-modalists deny that the Son is another rational individual being besides the Father, and so, they make Him the same rational individual being as the Father. The same being, then, the same person, according to the normal usage of the term, will then at once be made to be His own Father and His own Son, which is absurd; and while saying that He is both, they will actually make Him neither. So the one they call Son will relate to God, not as a Father, not as one individual being to another, Who is His Father, but will relate to God as His own self. By making the Son a mask and mode of the one God, they deny His real personal existence as a Son, which necessarily must be another rational individual being besides the one Whose Son He is. And so they deny the Lord, the Son of God, making Him a Son in name only and not in truth.
They say that the Father Who testifies to the Son is not another besides Him, but merely another mode of His own person, and so, they make the Son’s testimony false, for “If I bear witness of Myself, My witness is not true.” And so they make God out to be a liar.
Let this then serve as a warning of the deceitful equivocation of the heretics; for they will say that “God is three persons”, but the “God” they speak of is one person, one rational individual being, and the three “persons” they speak of are no persons at all, but mere masks, modes, roles, name, or internal relations of one person. They speak of a “triune God”, a “tripersonal God”, when in reality, the God they speak of, when they are honest, is only one person, and not three; and He has no true Son, the Son being made to be simply a mode of His own person, not another person Who relates to Him as a Father; and there will be no mediator to bring them to their “tripersonal God”, for having made their mediator to be nothing more than a mode of the very person they need a mediator to approach, they will have no true mediator, no third party, to bring them to God.