I want to invite you on an adventure into the mystery of this indispensable Christian doctrine. But instead of exploring eternal generation’s biblical warrant (see Simply Trinity: The Unmanipulated Father, Son, and Spirit for that exciting journey), we will take the road less traveled and press into this doctrine’s theological reasoning.

Let the adventure begin.

What is Eternal Generation?

The word generation means “coming forth,” and with reference to the Trinity it refers to the Son’s coming forth from the Father’s essence. The concept takes us to the very heart of what it means for the Son to be a Son. He is eternally from the Father, which is why He is called Son. To be more specific, from all eternity, the Father communicates the one, simple, undivided divine essence to the Son.

At the risk of stating the obvious, a son is, by definition, one who is generated by his father—one who has his origin from his father. While we will point out dissimilarities between human and divine sonship soon enough, we cannot miss the one fundamental similarity: sonship means one is generated by a father. When the concept is applied to the Son of God—as it so often is by the authors of Scripture—it means in its most basic sense that He, as the eternal Son, is from His Father.

To clarify, to be from the Father does not refer to the incarnation, to Christ as Mediator; being sent by the Father to save may reflect eternal generation, but it in no way constitutes eternal generation. Instead, to be from the Father refers to the Son’s origin in eternity, apart from creation. Generation is between Father and Son, an eternal act, and not between the Trinity and creation, as if it were a temporal act. As we will learn, generation is internal to the triune God—ad intra, as we like to say in Latin, as opposed to external, ad extra. The Father’s sending His Son into the world on mission for the world reflects the Son’s eternal origin from the Father (generation), but that mission in no way constitutes His eternal relation of origin. The Son is generated (begotten) by the Father before all ages apart from the world, irrespective of creation. He is Son whether or not He is ever sent into the world; He is the eternal Son from the Father whether or not He ever becomes incarnate. It is the immanent Trinity that is in view, not the economic.

There is another term that conveys the concept of generation: begotten. Perhaps you’ve heard the word used when reading those long genealogies in the Bible: so-and-so begat so-and-so begat so-and-so. But John applies this language to Jesus as well, referring to Him as the only begotten Son of God (e.g., John 1:14, 18; 3:16, 18). This begotten language, however, long predates the King James Bible. Way back in the fourth century, the church fathers who wrote the Nicene Creed used it as well. For example, the Nicene Creed says, “We believe in . . . one Lord Jesus Christ, the only-begotten Son of God, begotten from the Father before all time.”

This is the One, undivided God we are talking about; therefore, for the Son to be begotten from the Father means that God is begotten from God, which is why the creed confesses the Son to be “true God from true God.” To confess the Son as true God from true God is not an overstatement since He is, we dare not forget, consubstantial with the Father. Consubstantial means the Son is equal to the Father in every way, from the same essence or substance as the Father, no less divine than the Father.