Although the eternal generation of the Son is affirmed in early confessions such as the Nicene-Constantinopolitan creed (AD 381) and post-Reformation statements like the Westminster Confession, several prominent evangelical theologians object to this doctrine on the grounds that it lacks biblical support. Evangelicals who reject this doctrine frequently point out that the Greek word monogenes (John 1:18; 3:16) does not mean "only begotten" but rather "unique." Since the mistranslation of monogenes (allegedly) represents one of key lines of biblical evidence, one should dispense with eternal generation as a theological relic of a bygone era.
In light of this, how should we think about eternal generation?
Examining the Evidence
As a thought experiment, I decided to examine the evidence for eternal generation in the writings of one of the most important trinitarian theologians in the early church---Augustine of Hippo (354-430). I wanted to see how the Latin doctor approached the biblical and theological evidence for eternal generation. The results of my investigation are published in an essay titled "Augustine, Eternal Generation, and Evangelical Trinitarianism" Trinity Journal 32 NS (2011): 141-163.
As I explored his discussion, I discovered that Augustine's case for eternal generation does not depend on the mistranslation of monogenes but is deeply rooted in the way Scripture portrays the relation of the Son to the Father. I was surprised by the breadth of biblical evidence Augustine marshaled. Although one might assume that Augustine's commitment to eternal generation is merely rooted in a handful of dubious "proof texts," nothing could be further from the truth. This doctrine is rooted in a rigorous and comprehensive Trinitarian hermeneutic.
Two hermeneutical assumptions play an essential role in Augustine's case for eternal generation.
The first assumption concerns three ways Scripture speaks about Jesus Christ. According to Augustine, New Testament references to the person of Christ can be grouped into three categories: (1) texts that refer to Son in the "form of God" (divine nature) in which he is equal to the Father (e.g., Phil 2:6; John 10:30); (2) texts that refer to the Son in the "form of a servant" (human nature) in which he is "less" than the Father (e.g., John 14:28); and (3) texts that suggest that the Son is "from" the Father. This third category is crucial to Augustine's case for eternal generation. He argues that a distinction between the Son in the "form of God" and the "form of a servant" cannot encompass the rich way that Scripture speaks about the person Christ.
John 5:26 reflects this third category. "For as the Father has life in himself, so he has granted the Son also to have life in himself" (John 5:26). This passage teaches that the Father (v. 26a) possess "life in himself" (i.e., self-existence). We are told that the Son possesses a form of "life" identical to that of the Father---"life in himself" (v. 26b). The Father and Son, however, possess "life in himself" in distinct ways. The Son possesses "life in himself" that has been "given" to him while the Father possesses "life in himself" that was given by no one. How, Augustine asks, did the Son receive "life in himself"? His answer is both simple and profound: the Father "begat" the Son. According to Augustine, the phrase "has been given" (v. 26b) is roughly equivalent in meaning to "has been begotten."
Augustine's interpretation of the phrase "has been given" as "has been begotten" may strike some readers as a huge leap. It is important to remember that theologians frequently use terms not found in the biblical text (e.g., Trinity, person, essence, nature, and so on) in order to explain what the text affirms. For example, most theologians (including those who reject eternal generation) interpret "life" in v. 26 as referring to God's essence even though the term essence is not found in John 5:26. Here we see Augustine appealing to eternal generation in order to account for the theological judgment this text renders regarding the relation of the Son to the Father. He writes:
Therefore, the Father remains life, the Son also remains life; the Father, life in himself, not from the Son, the Son, life in himself, but from the Father. [The Son was] begotten by the Father to be life in himself, but the Father [is] life in himself, unbegotten (Tractates on the Gospel of John 19.13).
A second hermeneutical assumption relates to the reliability of God's self-revelation in Scripture. Augustine (rightly) believes that patterns of divine relation in the economy of salvation echo eternal relations among the divine persons. The economy of salvation (constituted by the missions of the Son and Holy Spirit) is not merely a record of the actions undertaken by God to save us. It is also designed to teach us about God. As Fred Sanders explains in his recent book on the Trinity, "God has given form and order to the history of salvation because he intends not only to save us through it but also to reveal himself through it. The economy is shaped by God's intention to communicate his identity and character" (The Deep Things of God: How the Trinity Changes Everything [Wheaton: Crossway, 2010], 133). Hence, when the Son and Holy Spirit appear, they behave as they truly are: "their eternal personalities, we might say, are exhibited here in time" (p. 151).
There are at least five areas where Augustine sees patterns in the economy of salvation offering a window into the unique nature of the Son's eternal relationship to the Father. I develop these in detail in my Trinity Journal article. Here I can only gesture toward them. The first group includes the numerous passages affirming that the Son was "sent" by the Father (e.g., Matt 10:40; Luke 4:43; 10:16; Gal 4:4-6; John 4:34; 5:23-24, 30-47; 6:38-44, 57; 7:16, 28-29, 33; 8:16-18, 26-29, 42; 9:4; 12:44-50; 13:16; 14:24; 15:21; 16:5, 28; 17:3, 18; 20:21). A second line of evidence includes passages that speak of the Father "giving" and the Son "receiving" (e.g., John 5:19, 22, 26, 27, 36; 10:18; 17:2, 8, 11, 22; 18:11). A third group includes passages that reflect an ordered equality that constitutes the working of the Father and Son---the Father works all things through the Son (John 1:1-3, 10; 5:19, 21; 14:6; Rom 5:1, 11; 1 Cor. 8:6; Eph 1:3-14; 2:18; 4:6; Col 1:16; 3:17; Heb 1:1-2; Jude 25). A fourth group of passages includes those that use the names "Father" and "Son" (e.g., Matt 11:27; 24:36-39; 28:18; Gal 4:4-6). A final group of texts supporting the eternal generation of the Son comes from an unlikely source---parallel passages about the relation of the Holy Spirit to the Son and Father (e.g., John 15:26; 16:13-14).
Although critics sometimes present this doctrine as if it depends on a handful of dubious proof texts, the biblical evidence for eternal generation is rooted in broad patterns of scriptural judgment regarding the unique nature of the eternal relationship of the Son to the Father. There is no undisputed proof-text for eternal generation. The question we must ask is, "What must be true of God in order to make sense of all these 'from another' passages?"