A Body of Divinity by Thomas Watson
Q-6. HOW MANY PERSONS ARE THERE IN THE GODHEAD?
A: Three persons, yet but one God.
'There are three that bear record in heaven, the Father, the Word, and the Holy Ghost, and these three are one. I John 5: 7.
God is but one, yet are there three distinct persons subsisting in one Godhead. This is a sacred mystery, which the light within man could never have discovered. As the two natures in Christ, yet but one person, is a wonder; so three persons, yet but one Godhead. Here is a great deep, the Father God, the Son God, the Holy Ghost God; yet not three Gods, but one God. The three persons in the blessed Trinity are distinguished, but not divided; three substances, but one essence. This is a divine riddle where one makes three, and three make one. Our narrow thoughts can no more comprehend the Trinity in Unity, than a nut-shell will hold all the water in the sea. Let me shadow it out by a similitude. In the body of the sun, there are the substance of the sun, the beams, and the heat; the beams are begotten of the sun, the heat proceeds both from the sun and the beams; but these three, though different, are not divided; they all three make but one sun: so in the blessed Trinity, the Son is begotten of the Father, the Holy Ghost proceeds from both; yet though they are three distinct persons, they are but one God. First, let me speak of the Unity in Trinity; then of the Trinity in Unity.
I. Of the Unity in Trinity. The Unity of the persons in the Godhead consists of two things.
[I] The identity of essence. In the Trinity there is a oneness in essence. The three persons are of the same divine nature and substance; so that in Deo nonest magis et minus, 'there are no degrees in the Godhead; one person is not God more than another.
 The Unity of the persons in the Godhead consists in the mutual inbeing of them, or their being in one together. The three persons are so united that one person is in another, and with another. 'Thou, Father, art in me, and I in thee. John 17: 2I.
II. Let me speak of the Trinity in Unity.
[I] The first person in the Trinity is God the Father. He is called the first person, in respect of order, not dignity: for God the Father has no essential perfection which the other persons have not; he is not more wise, more holy, more powerful than the other persons are. There is a priority, not a superiority.
 The second person in the Trinity is Jesus Christ, who is begotten of the Father before all time. 'I was set up from everlasting, from the beginning, or ever the earth was. When there were no depths I was brought forth; when there were no fountains abounding with water. Before the mountains were settled, before the hills, was I brought forth. Prov 8: 23 - 25. This Scripture declares the eternal generation of the Son of God. This second person in the Trinity, who is Jehovah, is become our Jesus. The Scripture calls him the branch of David, Jer 23: 5, and I may call him the flower of our nature. 'By him all that believe are justified. Acts 13: 39.
 The third person in the Trinity is the Holy Ghost, who proceeds from the Father and the Son, whose work is to illuminate the mind, and enkindle sacred motions. The essence of the Spirit is in heaven, and everywhere; but the influence of it is in the hearts of believers. This is that blessed Spirit who gives us the holy unction. 1 John 2: 20. Though Christ merits grace for us, it is the Holy Ghost that works it in us. Though Christ makes the purchase, it is the Holy Ghost that makes the assurance, and seals us to the day of redemption. Thus I have spoken of all the three persons. The Trinity of persons may be proved out of Matt 3: I6. 'Jesus, when he was baptized, went up straightway out of the water, and he saw the Spirit of God descending like a dove, and lighting upon him; and lo, a voice from heaven, saying, This is my beloved Son.' Here are three names given to the three persons. He who spake with a voice from heaven was God the Father; he who was baptized in Jordan was God the Son; he who descended in the likeness of a dove was God the Holy Ghost. Thus I have shown you the Unity of essence, and the Trinity of persons.
Use one: For confutation. (I.) This confutes the Jews and Turks, who believe only the first person in the Godhead. Take away the distinction of the persons in the Trinity, and you overthrow man's redemption; for God the Father being offended with man for sin, how shall he be pacified without a mediator? This mediator is Christ, who makes our peace. Christ having died, and shed his blood, how shall this blood be applied but by the Holy Ghost? Therefore, if there be not three persons in the Godhead, man's salvation cannot be wrought out; if there be no second person in the Trinity, there is no redeemer; if no third person, there is no comforter. Thus the plank is taken away by which we get to heaven.
(2.) It confutes the execrable opinion of the Socinians, who deny the Divinity of the Lord Jesus, and make him to be a creature only, but of a higher rank. As the Papists blot out the second commandment, so the Socinians do the second person in the Trinity. If to oppose Christ's members be a sin, what is it to oppose Christ himself? Jesus Christ is co-equal with God the Father. He thought it no robbery to be equal with God. Phil 2: 6. He is co-eternal with God the Father: 'I was from the beginning, Prov 8: 23: if not, there was a time when God was without a Son, and so he would be no Father; nay, there was a time when God was without his glory, for Christ is 'the brightness of his Fathers glory. Heb 1: 3. He is co-essential with God the Father. The Godhead subsists in Christ. 'In whom dwells all the fulness of the Godhead bodily.' Col 2: 9. It is said, not only that Christ was with God before the beginning, but that he was God. John 1: I, and 1 Tim 3: I6. 'God manifest in the flesh.' The title of Lord, so often given to Christ, in the New Testament, answers to the title of Jehovah in the Old. Deut 6: s; Matt 22: 37. Christ has a co-eternity, and co-substantiality with his Father. 'I and my Father are one. John 10: 30. It were blasphemy for an angel to speak thus. Yet further to prove Christs Godhead, consider (i) The glorious incommunicable attributes belonging to God the Father are ascribed to Christ. Is God the Father omnipotent? So is Jesus Christ. He is the almighty, Rev 1: 8, and he creates, Col 1: I6. Is God the Father infinitely immense, filling all places? Jer 23: 24. So is Jesus Christ. While Christ was on the earth by his bodily presence, he was at the same time in the bosom of the Father by his divine presence. John 3: I3. (ii) The same jura regalia, or prerogatives royal, which belong to God the Father, belong also to Christ. Does God the Father seal pardons? This is a flower of Christ's crown. 'Thy sins be forgiven thee.' Matt 9: 2. Nor does Christ remit sin organice only, as ministers do, by virtue of a power delegated to them from God; but he does it by his own power and authority. Is God the Father the adequate object of faith? Is he to be believed in? So is his Son. John 14: 1. Does adoration belong to God the Father? So it does to the Son. 'Let all the angels of God worship him.' Heb 1: 6. How sacrilegious therefore is the Socinian, who would rob Christ of his Godhead, the best flower of his crown. They that deny Christ to be God, must greatly wrest, or else deny the Scripture to be the Word of God.
(3.) It confutes the Arians, who deny the Holy Ghost to be God. The eternal Godhead subsists in the Holy Ghost. 'He shall guide you into all truth.' John 16: I3. Christ speaks not there of an attribute, but of a person. That the Godhead subsists in the person of the Holy Ghost appears in this; that the Spirit, who gives diversity of gifts, is said to be the same Lord, and the same God. I Cor 12: 5, 6. The black and unpardonable sin is said, in a special manner, to be committed against the Godhead subsisting in the Holy Ghost. Matt 12: 32. The mighty power of God is made manifest by the Holy Ghost; for he changes the hearts of men. The devil would have Christ prove himself to be God, by turning stones into bread; but the Holy Ghost shows his Godhead by turning stones into flesh. 'I will take away the stony heart; and give you a heart of flesh.' Ezek 36: 26. Yet further, the power and Godhead of the Holy Ghost appeared in effecting the glorious conception of our Lord Jesus Christ. The very shadow of the Holy Ghost made a virgin conceive. Luke 1: 35. The Holy Ghost works miracles, which transcend the sphere of nature; as raising the dead. Rom 8: 11. To him belongs divine worship; our souls and bodies are the temples of the Holy Ghost, I Cor 6: I9, in which temples he is to be worshipped, verse 20. We are baptized in the name of the Holy Ghost; therefore we must believe his Godhead, or renounce our baptism in his name. Methinks it were better for such men not to have so much as heard whether there be any Holy Ghost, Acts 19: 2, than to deny his Deity. They who would wittingly and willingly blot out the third person, shall have their names blotted out of the book of life.
Use two: For exhortation. (I.) Believe this doctrine of the Trinity of persons in the unity of essence. The Trinity is purely an object of faith; the plumbline of reason is too short to fathom this mystery; but where reason cannot wade, there faith may swim. There are some truths in religion that may be demonstrated by reason; as that there is a God: but the Trinity of persons in the Unity of essence is wholly supernatural, and must be believed by faith. This sacred doctrine is not against reason, but above it. Those illuminated philosophers, that could find out the causes of things, and discourse of the magnitude and influence of the stars, the nature of minerals, could never, by their deepest search, find out the mystery of the Trinity. This is of divine revelation, and must be adored with humble believing. We can be no good Christians, without the firm belief of the Trinity. How can we pray to God the Father but in the name of Christ, and through the help of the Spirit? How believe the glorious Trinity? How are the Quakers to be abhorred, who go under the name of Christians, and yet undervalue and renounce Jesus Christ! I have read of some Quakers who speak thus: 'We deny the person of him whom you call Christ, and affirm, That they who expect to be saved by that Christ without works, will be damned in that faith! Could the devil himself speak worse blasphemy? They would pull up all religion by the roots, and take away that corner stone, on which the hope of our salvation is built.
(2.) If there be one God subsisting in three persons, then let us give equal reverence to all the persons in the Trinity. There is not more or less in the Trinity; the Father is not more God than the Son and Holy Ghost. There is an order in the Godhead, but no degrees; one person has not a majority or supereminence above another, therefore we must give equal worship to all the persons. 'That all men should honour the Son even as they honour the Father.' John 5: 23. Adore Unity in Trinity.
(3.) Obey all the persons in the blessed Trinity; for all of them are God. Obey God the Father. Christ himself, as man, obeyed God the Father, John 4: 34, much more must we. Deut 27: 10.
Obey God the Son. 'Kiss the Son, lest he be angry.' Psa 2: I2. Kiss him with a kiss of obedience. Christ's commands are not grievous. I John 5: 3. Whatever he commands is for our interest and benefit. Oh then kiss the Son! Why do the elders throw down their crowns at the feet of Christ, and fall down before the Lamb? Rev 4: 10, 11. To testify their subjection, and to profess their readiness to serve and obey him.
Obey God the Holy Ghost. Our souls are breathed into us by the glorious Spirit. 'The Spirit of God has made me. Job 33: 4. Our souls are adorned by the blessed Spirit. Every grace is a divine spark lighted in the soul by the Holy Ghost. Nay, more, the Spirit of God sanctified Christs human nature; he united it with the divine, and fitted the man Christ to be our Mediator. Well then does this third person in the Trinity, the Holy Ghost, deserve to be obeyed; for he is God, and this tribute of homage and obedience is due to him from us.
From A Body of Divinity. Published by Banner of Truth Trust.