The Eternally Begotten Son Is Consubstantial With the Father

The Son’s generation involves no priority or posteriority, and certainly no inferiority but designates order alone. If it did involve priority or posteriority of any kind, then the Son would be inferior to the Father.

Previously, I emphasized that the Son is begotten by the Father, but unlike our human experience, the Son’s generation is eternal (before all ages, timeless). And if eternal, then the generation of the Son is not the generation of a lesser being (made in time or before time) but the generation of a Son who is equal in deity to His Father. But the reason the Son is not inferior to the Father is because the one divine essence wholly subsists in the Son due to His generation from the Father’s nature or substance. As the Son is true God from true God, there can be “no diminution of the Begetter’s substance” in the generation of the Son.1 The Father begets His Son, and the two are, to return to that key word from Nicaea, consubstantial, meaning they are to be identified by the self-same divine essence. Priority or posteriority would undermine the Son as consubstantial, as One who is of the same nature as the Father.

As we’ve learned, the lack of priority or posteriority is due in part to the timeless nature of the Son’s generation, which is eternal, not temporal. Gregory of Nazianzus was once asked why the Son and the Spirit are not co-unoriginate along with the Father if it is true that they are coeternal with the Father. His response: “Because they [Son and Spirit] are from him [Father], though not after him. ‘Being unoriginate’ necessarily implies ‘being eternal,’ but ‘being eternal’ does not entail ‘being unoriginated,’ so long as the Father is referred to as origin.” To drive this point home, Gregory appealed to the illustration of the sun. “So because they [Son and Spirit] have a cause they are not unoriginated. But clearly a cause is not necessarily prior to its effect—the Sun is not prior to its light. Because time is not involved, they are to that extent unoriginated—even if you do scare simple souls with the bogey-word; for the sources of time are not subject to time.”2

With a nudge from Gregory, consider the biblical imagery of light (John 1:4, 8–9). The Nicene Creed says the Son’s eternal generation from the Father can be compared to “light from light.” The Cappadocian Fathers (Basil the Great, Gregory of Nyssa, and Gregory of Nazianzus—key fourth-century church fathers who helped clarify our doctrine of the Trinity) also appealed to this imagery of light to counter the belief of subordinationists who said an effect is inferior to its cause, the Son subordinate to the Father. Consider the sun, they said in response. It is the cause of light, but by no means is light inferior to its source. In essence, they are one and the same. How much more so with divinity? Is not the divine essence simple and inseparable, eternal, and immutable? Read more»

Matthew Barrett, “Undivided Trinity,” Table Talk (May 19, 2021)


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  • R. Scott Clark
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    R.Scott Clark is the President of the Heidelberg Reformation Association, the author and editor of, and contributor to several books and the author of many articles. He has taught church history and historical theology since 1997 at Westminster Seminary California. He has also taught at Wheaton College, Reformed Theological Seminary, and Concordia University. He has hosted the Heidelblog since 2007.

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