Greg Koukl
Author Greg Koukl
Published on 12/22/2025
Theology

Why Is It Important that Jesus Be Both God and Man?

Greg and Amy draw from Hebrews and the Old Testament concept of the kinship redeemer to show how Jesus stands in solidarity with us while remaining morally capable of redeeming us. Through the incarnation, God remains just while justifying those who trust in Jesus.


Transcript

Amy: Let’s go to a question from Lucy. Why is it important for Jesus Christ to be both fully God and fully man?

Greg: Wow, we’re getting the heavy duty ones now. There was a piece that was written—there are two I’m thinking of right now, and I can only think of the title of one. One’s by Athanasius in the fourth century and the other one was—I’ll think of the name in a bit, but it was right around the turn of the first millennium. And one of them was called Why the God-Man? and it made the case why it was necessary. And I do this also in The Story of Reality, but it’s a much more modest kind of characterization. To put it simply, I guess, since man fell and was guilty, the guilt had to be paid by man, but an ordinary man could not pay the penalty for everybody. And that’s why it had to be God made flesh that could pay in a finite amount of time the penalty for sin that an individual would spend forever paying for in Hell.

So, okay, that’s a strange calculus. Yeah, you’re right. It is. But that seems to be the—I think there’s a—in Hebrews, it says, and again this is a snatch of a verse, something about since the brethren partook of flesh and blood, so the Son had to partake of flesh and blood also. And there’s this concept of the kinship redeemer in the Old Testament. You have somebody that needs to be redeemed, purchased out of a situation. I mean, oftentimes redemption is talking about slavery. But kinship redeemer applied to different things like Ruth, where that was played out in the Old Testament. But it had to be some kin, and in this case where Jesus is redeeming us, he redeems us in that sense, kinship redeemer, as another human being. And so, a human who is not a slave is able to redeem those humans who are. And since humans, in a certain sense, gave in to the devil, it’s a human champion of sorts that now defeats the devil. So, there’s a way that these all kind of interact. But the biggest thing has to do with the capability of a mere human to pay for the sins of mankind. And a mere human couldn’t do that.

So, you have Why the God-Man? Oh, Amy, you’re supposed to help me with this.

Amy: On the Incarnation?

Greg: There you go. That’s Athanasius. On the Incarnation. That’s Athanasius. And this is available. You can probably find it online. And then Why the God-Man? And the name of this particular theologian philosopher slips my mind. He was very big in substitutionary atonement.

Amy: Is it Anselm?

Greg: Yeah, I think it is Anselm. Good. Cur Deus Homo. The Latin Cur Deus Homo, which means Why the God-Man? And then he develops—and I’ve read this piece. It’s really magnificent. And not everybody agrees with it, but he does offer a rationale about how this is the case and why a substitute is necessary, and the substitute has to be somebody adequate to the task—has to be human but also has to be divine to accomplish the task before him.

Amy: And sinless.

Greg: And not a slave himself.

Amy: Right. What’s the word I’m looking for? Infinitely valuable.

Greg: Don’t ask me. I’m looking to you for the words here.

Amy: And Hebrews also says the priests in the Old Testament had to first pay for their own sins and then others. But Jesus came. He didn’t have to pay for his own sins because he was sinless, and that’s why he was able to pay for the sins of others. And you can’t do that unless you’re perfect. You can’t be a fallen man. You have to be the perfect God-man.

Greg: There’s another little detail here, Lucy, that this isn’t just, well, that’s the way he did it, and that’s what he says. Now, you could tell me the reference here—it’s probably in Romans—where it says God is both the just and the justifier of him who has faith in Jesus. So, he can accomplish justice, but he can also then justify, that is, credit righteousness and save the one who puts their faith in Jesus.

Amy: So, that’s another reason. It’s beautiful, and it reveals who God is. By Jesus coming as the second person of the Trinity, he’s showing a loving self-sacrifice and a love for enemies, and that’s revealing something about God’s grace and his glory. So, all of this had a purpose, and part of the purpose—I mean, I think the main purpose—was to reveal God to his people. And so, this all played—there was a reason for all of this. It wasn’t just random. And it wasn’t just about a transaction. I think it was also about revealing the beauty of who God is.

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