And so, the orthodox doctrine of the Trinity — which is summarized by the confession that God is one, and that this one God eternally subsists in three co-equal and consubstantial persons, the Father, the Son, and the Holy Spirit, which persons, though distinct from one another, each fully possess the undivided divine essence — is not an unbiblical concoction devised by human reasoning and philosophical speculation. It is biblical, even though the words “Trinity” and “essence” and “subsistence” don’t appear in Scripture. By teaching that God is one, and that the Father is God, the Son is God, and the Spirit is God, Scripture shuts us up to Trinitarianism.
During the Arian controversy of the fourth century, the Arians employed many arguments against the doctrines of the Trinity and the Deity of Christ. Perhaps one of the most popular arguments was that men like Athanasius were using unbiblical terminology to describe the nature of God and the person of Christ. The famous word homoousios — i.e., “same substance,” indicating that the Son was of the same substance of the Father, not merely of similar substance — was nowhere to be found in Scripture, while the Arians insisted upon the “plain sense” of texts like John 14:28 , where Jesus confesses, “The Father is greater than I.” In the sixteenth century, the anti-Trinitarian Socinians leveled this same argument against historic orthodoxy. “Trinity” was a word that was absent from the Bible. The Reformed Orthodox were simply imbibing man-made tradition, whereas they (the Socinians) were aiming to be true to Scripture by using strictly biblical language.
John Owen saw it as a personal calling to answer the numerous heresies of Socinianism, and the church has been the richer for his efforts. Early on in his “A Brief Declaration and Vindication of The Doctrine of the Trinity,” Owen answers this common objection, and explains why employing extrabiblical terms like “substance,” “subsistence,” and “Trinity” is not only permissible but necessary for faithful biblical interpretation and theological discussion. He writes:
“And herein [i.e., in discussing the Trinity], as in the application of all other divine truths and mysteries whatever, yea, of all moral commanded duties, use is to be made of such words and expressions as, it may be, are not literally and formally contained in Scripture; but only are, unto our conceptions and apprehensions, expository of what is so contained.
“And to deny the liberty, yea, the necessity hereof, is to deny all interpretation of the Scripture, — all endeavors to express the sense of the words of it unto the understandings of one another; which is, in a word, to render the Scripture itself altogether useless.
“For if it be unlawful for me to speak or write what I conceive to be the sense of the words of the Scripture, and the nature of the thing signified and expressed by them, it is unlawful for me, also, to think or conceive in my mind what is the sense of the words or nature of the things; which to say, is to make brutes of ourselves, and to frustrate the whole design of God in giving unto us the great privilege of his word.
“Wherefore, in the declaration of the doctrine of the Trinity, we may lawfully, nay, we must necessarily, make use of other words, phrases, and expressions than what are literally and syllabically contained in the Scripture, but teach no other things.
“Moreover, whatever is so revealed in the Scripture is no less true and divine as to whatever necessarily followeth thereon, than it is as unto that which is principally revealed and directly expressed. For how far soever the lines be drawn and extended, from truth nothing can follow and ensue but what is true also; and that in the same kind of truth with that which it is derived and deduced from. For if the principal assertion be a truth of divine revelation, so is also whatever is included therein, and which may be rightly from thence collected.
“Hence it follows, that when the Scripture reveals the Father, Son, and Holy Ghost to be one God, seeing it necessarily and unavoidably follows thereon that they are one in essence (wherein alone it is possible they can be one), and three in their distinct subsistences (wherein alone it is possible they can be three), — this is no less of divine revelation than the first principle from whence these things follow.”