What is partialism in relation to the Trinity?

Nor is this truth to be enfeebled in the least degree. He who allows no more in the Godhead than three aspects of one Person is not a Christian, but a deceiver and an antichrist. He does not confess the fully revealed and true God, not the Godhead merely in three characters but in Three Persons; and so distinct that the Father could send the Son (1 John 4:14), and the Holy Ghost descend on that Son in the presence of the Father and in the consciousness of the Son (Mark 1:10-11), as it was even outwardly before man also (John 1:33-34).

Nor is this truth to be enfeebled in the least degree. He who allows no more in the Godhead than three aspects of one Person is not a Christian, but a deceiver and an antichrist. He does not confess the fully revealed and true God, not the Godhead merely in three characters but in Three Persons; and so distinct that the Father could send the Son (1 John 4:14), and the Holy Ghost descend on that Son in the presence of the Father and in the consciousness of the Son (Mark 1:10, 11), as it was even outwardly before man also (John 1:33, 34).

Nor is this truth to be enfeebled in the least degree. He who allows no more in the Godhead than three aspects of one Person is not a Christian, but a deceiver and an antichrist. He does not confess the fully revealed and true God, not the Godhead merely in three characters but in Three Persons; and so distinct that the Father could send the Son (1 John 4:14), and the Holy Ghost descend on that Son in the presence of the Father and in the consciousness of the Son (Mark 1:10, 11), as it was even outwardly before man also (John 1:33, 34).

One is Tritheism, or setting up three distinct Gods; the other,

Sabellianism, which holds that there is but one God under three different names.

As a matter of fact, instead of being new light, it is a very old error, an error which, from time to time, has gained a new Lease of life, so that there is nothing new about it at all. It is really Sabellianism, only perhaps under a new guise. This early teacher, in opposition to Tritheism, maintained there was only one God, but that He sometimes acted "as Father, sometimes as Son, sometimes as Spirit, and sometimes as all three."

Those who propagate such views have been accused of what is known as Sabellianism. This is a mistake. Sabellius of N. Africa (200 A.D.) taught that God is essentially Uni-personal, and that what we speak of as three Personal Subsistencies in the Unity of the Godhead, were really only threefold in manifestation; that the same Person, as Father, purposed to save; as Son, accomplished redemption, and, as Holy Spirit, came to lead sinners to Christ. Popular illustrations of the "Three in One"—from the nature of light or the mode of existence of certain substances are essentially Sabellian and should be avoided. Such teaching is of course fundamentally unsound. But the special denials combated here lend themselves more to tritheism. Instead of a past eternity and an Old and a New Testament, full of the relations of three Divine Persons in the Unity of the Godhead in intimate relation one to another, as Father, Son and Spirit (and no other possible relation is suggested), we are told to think of three Divine Beings, how related is not revealed, in a cold, colourless, blank eternity as far as Divine affections are concerned. Beings all the replica one of another, and of course without any subordination for mutual purposes, which in their shallow way these errorists declare to be incompatible, "if words mean anything," a favourite phrase of their school, with the equality of the Divine Persons, as they understand the phrase.

When I say it is by necessity of nature, I do not mean that the divine nature, in which the divine Persons subsist, distinguishes Them; for that nature is one and common to Them all. The nature of the Son is the same with that of the Father; and the nature of the Spirit the same with that of the Father and the Son; and this nature, which They in common partake of, is undivided; it is not parted between Them, so that one has one part, and another a second, and another a third; nor that one has a greater and another a lesser part, which might distinguish Them, but the whole fullness of the Godhead is in each.

“To come to the point—it is the personal relations or distinctive relative properties which belong to each Person which distinguish Them from one another; as paternity in the First Person, filiation in the Second, and spiration in the Third; or, more plainly, it is begetting Psalm 2:7 which peculiarly belongs to the First, and is never ascribed to the Second and Third, which distinguishes Him from Them both, and gives Him; with great propriety, the Name of the Father; and it is being begotten, that is the personal relation, or relative property of the Second Person, hence called the only begotten of the Father (John 1:14), which distinguishes Him from the First and Third, and gives Him the name of the Son; and the relative property, or personal relation of the Third Person is, that He is breathed by the First and Second Persons; hence called the breath of the Almighty, the breath of the mouth of Jehovah the Father, and the breath of the mouth of Christ the Lord, and which is never said of the other Two Persons, and so distinguishes Him from Them; and very pertinently gives Him the name of the Spirit, or breath” (Job 33:4; Psalm 33:6; 2 Thessalonians 2:8). “Body of Divinity,” Book 1., ch. 28.

“This nature is common to the Three Persons in God, but not communicated from one to another; They each of Them partake of it, and possess it as one undivided nature; They all enjoy it; it is not a part of it that is enjoyed by one, and a part of it by another, but the whole by each; as all the fullness of the God-head dwells in Christ, so in the Holy Spirit; and of the Father there will be no doubt; these equally subsist in the unity of the divine Essence, and that with out any derivation or communication of it from one to another. I know it is represented by some who otherwise are sound in the doctrine of the Trinity, that the divine nature is communicated from the Father to the Son and Spirit, and that He is fons Deitatis, ‘ the fountain of Deity,’ which I think are unsafe phrases, since they seem to imply a priority in the Father to the other Two Persons; for He that communicates must, at least, in order of nature and according to our conception of things, be prior to whom the communication is made; and that He has a superabundant plenitude of Deity in Him, previous to this communication. It is better to say that They are self-existent, and exist together in the same undivided Essence; and jointly, equally, and as early one as the other, possess the same nature.”—”Body of Divinity,” Book 1., Chap. 4. [There is an excellent summary of the Doctor's views on these points in the Memoir of Dr. Gill, prefixed to Mr. Doudney's edition of his Commentary on the Old Testament, vol. 1. p. 26] The Essence of God, then, as thus ably and clearly explained, is that by which He exists; and as there can be but one God, and He is necessarily self-existent, His Essence is clearly distinct from the modes of subsistence of the Three Persons in the Godhead. The adversaries of the eternal Sonship of our blessed Lord, we will not say designedly, but probably through misconception, would represent our views somewhat in the following light, which, however, we put forward with considerable reluctance, as on a subject so holy and. sacred we dare not to think, much more to speak in any way derogatory to the glory of a Triune Jehovah. They would represent us, then, as holding that first there existed the Father alone; that He begat another God, whom we call the Son; and that from the Father and Son there proceeded another God, whom we call the Holy Spirit. But this perversion of truth is not our doctrine, nor can any such conclusion be legitimately deduced from our views. It may serve their purpose to seek to overthrow the scriptural doctrine of the eternal Sonship of the adorable Redeemer, by dressing up our views in a garb of their own manufacturing, or passing off their illegitimate progeny as our true-born offspring; but we refuse the dress which they would put upon their back, and disavow the children which they would lay at our door. It does not follow because the Lord Jesus Christ is the only-begotten Son of God in His divine nature, that He is “a begotten God.”

Thus we see that there could be no full revelation of God, but through the Son by the Spirit, and thereby of the Father. The full revelation of the one God is only thus - Father, Son, and Holy Ghost. This, this only, is what the one God is, one identity of will and being, so that they are essentially one and one only, yet distinct in willing and acting (and we can distinguish them in willing and acting: hence we commonly speak of persons), yet never willing or acting but in the common will and unity of nature.

There are three divine persons: the Father, the Son and the Holy Spirit. Each of them is ‘God’.

For the Son, see questions 2 and 3. For the Father, there are so many references to Him as the ‘God and Father’ (e.g. Eph. 1:3). The Spirit is eternal (Heb. 9:14), omnipresent (Ps. 139:7) and co-equal (‘on the same level with’) the Father and the Son (Mt. 18:19; 2 Cor. 13:13; Rev.1:4).