Section 3: The Unity of the Godhead proved, from the Unity of the Nature and Essence of the Father, Son, and Holy Spirit.

Book 1 Part 1 Chapter 2 Section 3 (p. 40-42)
The Unity of the Godhead proved, from the Unity of the Nature and Essence of the Father, Son, and Holy Spirit.

As Christian Doctrine knoweth but one only true God, so it recommendeth us for the most ample discovery (attainable in this World) of this One and Eternal Godhead, unto the Name of Father, Son, and Holy Spirit, which some call the Trinity, a Phrase no way offensive to Christianity; yet, as some of the [Calvin. Institutes] Ancients, well observe. It is not necessary to impose words upon any Man which God himself hath not used, by which to make known himself. Yet truly this term, The Trinity, hath very near affinity with the Language of the Holy Ghost. 1 John 5.7. "There are three which bear Record in Heaven, the Father, the Word, and the Holy Ghost; there three one One." We shall therefore briefly speak of the Unity of these Three, in respect of their Nature or Essence; which must either be the same, or else we endanger to rush upon that great Error, viz. to hold two Principles, Beginnings, or first Causes, in distinct Natures; and if we admit two, we may admit twenty, yea, ad infinitum; or if this be avoided, we must deny the Eternity of the Son and Holy Spirit, which is contrary to the Word of God, and the best Antiquity next that of the Holy Scriptures. But that the Son (I speak now in respect of his Divine Essence only) and the Holy Spirit are Eternal, as the Father is Eternal, or consequently of the same Nature or Essence, may be gathered from these Testimonies, Col. 1.16, 17. "For by him were all things created that are in Heaven, and that are in Earth, Visible and Invisible, whether they be Thrones, or Dominions, or Principalities, or Powers; all things were created by him, and for him: And he is before all things, and by him all things consist." These things are spoken of the Son of God, as appeareth vers. 15. who is expressly said, not only to be before all things, but him also by whom all things were created; and therefore himself was not created, and consequently he is Eternal. For two things only come under consideration in this case; Either he had his beginning in Time, or else is Eternal: That he had not his beginning in time, hear what himself saith Rev. 1.8 compared with vers. 17, 28. "I am Alpha and Omega, the beginning and the ending, which is, and which was, and which is to come, the Almighty." The very same words which are used by the Father himself, to demonstrate his Eternity, Isa. 41.4. "I the Lord First, and with the Last I am he." Again, Isa. 44.6. "I am the First, and I am the Last, and beside me there is no God." Thus we have the same Testimony, or manner of Speech to reveal to us, the Eternity of Christ as that of the Father. We have yet a further Evidence, John. 1.1, &c. "In the beginning was the Word, and the Word, and the Word was with God, and the Word was God. The same was in the beginning with God; All things were made by him, and without him was not any thing made that was made." The things to be noted here (as to the Point in hand) are still, that Christ is the Maker of all things, therefore himself was not made; he was with God in the beginning, even as God was in the beginning; yea, he was God in the beginning, and is openly called the Beginning it self, even as God is said to be the First, as before is shewed.

Again, Heb. 1.2, 8. Christ is called the express Image of his Fathers Person, or rather the express Character of his Substance, και χαρακτηρ της υποστασεως αυτου, Character substantia, as Montanus. Whence his Godhead is truly inferred, sith neither of the Angels, or any Created thing; For unto what shall we liken God, or where-with shall he be compared? But of the Son 'tis said, "Who being in the form of God, thought is not Robbery to be like, or equal with God"; and hence his Godhead is further declared, and therefore his Eternity, do also prove his Godhead, so the Testimonies which prove his Godhead, do prove his Eternity; and thence is concluded, that he is of one Essence with the God and Father of our Lord Jesus Christ. When therefore it is said, ver. 8. "Thy Throne, O God, is for ever and ever": There is both his Godhead and Eternity asserted, with as much clearness, as the Eternity of the Father is asserted, Psal. 90.1. "From everlasting to everlasting, thou art God." And the like followeth of these words, "Thou Lord, in the beginning laid the foundation of the Earth, and the Heavens are the Works of thy Hands," Heb. 1.10. with as much truth and clearness, as if we should prove the Eternity and Godhead of the Father, by Gen. 1.1. "In the beginning God created Heaven and Earth"; which I suppose is allowed a cogent Evidence in that respect.

See a full place to this purpose, Mat. 5.2. "His going forth hath been of old from everlasting."