No, Jesus could not have sinned, but he was genuinely tempted

Could Jesus have sinned? Yes - but wonderfully he didn’t & now gloriously he can’t: ‘When Hebrews tells us he can sympathize with us as our High Priest, we have to trust that Jesus actually experienced temptation.’
https://t.co/1mi1MrWOgf

— John Stevens (@_JohnStevens) May 13, 2022

Contrary to what John Stevens said in his tweet, I believe that Jesus was impeccable. Not only was he without sin, it was impossible for him to sin. Yet I also insist that Christ was not impervious to temptation. He 'suffered, when tempted' (Hebrews 2:18), experiencing the full force of Satan's attacks. How can both those points be true? 

1. The incarnate Son was a divine person with a human nature 

At the incarnation the Son of God took a human nature into union with himself. That personal union is unbreakable. For Jesus to have sinned his human nature would have needed to be able to detach itself from the person of the Son, for the Son as God cannot be party to sin.

The human nature of Jesus cannot act independently of the Son, for it is his human nature. Speaking abstractly, Christ's human nature is impersonal. It his no personhood of its own. But speaking concretely of the incarnate Christ, his human nature was in-personal. It existed in union with the person of the Son from the moment of its conception by the Holy Spirit in Mary's womb.  With that in mind we do not say that the human nature of the Son died for our  sins, but that the Son of God died for us in the mode of his human nature.

That is why Christ cannot sin according to either nature; divine or human. The two natures are united in the person of the Son. To say otherwise and suggest that the human nature could act independently smacks of Nestorianism, the idea that the incarnate Son was an alliance of two persons, divine and human, rather than a divine person with a human nature. 

Donald Macleod cites W. G. T. Shedd to this end, saying, 'When the Logos goes into union with a human nature, so as to constitute a single person with it, he becomes responsible for all that this person does through the instrumentality of this nature... Should Jesus Christ sin, the incarnate God would sin.' (The Person of Christ, IVP, 1988, p. 230). Similarly, Oliver Crisp spells out the logical implication of holding that while Christ was sinless, he could have sinned, 'In short, if Christ really could have sinned - but did not - then he must have been able to choose to sin as the God-Man. (God Incarnate: Explorations in Christology, T&T Clark, 2009, p. 134). 

2. The Father promised the incarnate Son the help of the Holy Spirit 

Jesus was conceived in the virgin's womb by the power of the Spirit so that the nature he assumed might be fully human and yet without sin, Luke 1:35. Also, the Father promised his Son the empowering presence of the Holy Spirit to enable him to accomplish the work of redemption, Isaiah 42:1, 61:1, Luke 3:21-22. The Holy Spirit empowered Jesus to live in obedience to the Father's will, that he might offer himself without blemish to God, Heb 9:13-14. 

It is inconceivable that Jesus could have sinned, as that would have constituted a massive failure in the work of the Spirit of God whom Christ received without measure from the Father. Not only the indissoluble union of Son to his human nature, but also the inseparable operations of the Trinity stand against the idea that Jesus could have sinned.

3. What the Son could not do as God he could do as man, but not sin

The incarnate Son did many things that God in himself could not do. That is the point of the incarnation. For human beings to be saved it was necessary for the Son to become man to suffer and die in our place. It fully consistent with God's character for the Son to become man to redeem us by his blood. Indeed, the cross is the great revelation of God's justice and love, Romans 3:25-26, 5:8. But it would have been inconsistent with God's character had Jesus sinned. God is love, but he also light and in him there is no darkness at all, 1 John 1:5. Again, Donald Macleod this time in his own words, 

We may link the subject 'God' with many predicates. The Son of God may suffer, be tempted, may be ignorant and may even die. But we cannot link God with the predicate 'sin'. God cannot in any situation or for any purpose commit a transgression of his own will. He absolutely cannot be guilty of lawlessness. (The Person of Christ, p. 230). 

4. The the incarnate Son needed no capacity to sin to be truly human 

In the original article tweeted by Stevens, Matthew Corey asks, "What kind of humanity is Jesus redeeming if there is no capacity for sin?" (Unionized Perfection). This assumes that having a capacity to sin is a mark of authentic humanity. Presumably resurrected and glorified humanity will be incapable of sinning. That does not mean that in saving us God rescues us from being human, rather than redeeming humanity from its fallen state.  As Robert Letham points out,

If the quintessence of being human is found in heaven and consists., among other things, in freedom from the possibility of sinning, it follows that impeccability itself does not undermine the humanity of Christ in his state of incarnate weakness prior to the resurrection. (Systematic Theology, Crossway, 2019, p. 525)

Jesus was the 'Word made flesh' (John 1:14). He came, said Paul 'in the likeness of sinful flesh and for sin' (Romans 8:3). The flesh he assumed was weak and mortal like ours, but it was the flesh of the Son of God and so was incapable of sinning for the reasons already given. Corey questions, 'If Jesus has no capacity for sin how was able to “become sin for us” (2 Cor 5:21).' But this it a category mistake. Paul was not saying that Jesus  "became capable of sinning for us" by virtue of his incarnation. Rather, he 'who knew no sin' bore the judicial penalty of sin on behalf of his people that 'so that in him we might become the righteousness of God'. Similarly in Romans 8:3, driving idea is the judicial condemnation of sin in Christ's flesh, not that he had a capacity for sin, 'by sending his own Son in the likeness of sinful flesh and for sin, he [God] condemned sin in the flesh'. 

Robert Letham concludes his discussion of whether it possible for Jesus to sin saying,  'that since a sinful condition is not essential to human nature, the argument that impeccability undermines the reality of Christ's humanity and the genuineness of his temptations fails.' (Systematic Theology, p. 526). 

5. The incarnate Son was impeccable, but not impervious to temptation

The incarnate Son was impeccable from the moment of his conception. But that does not mean he was impervious to temptation, Luke 4:1-13, Hebrews 2:18. Adam was so made that it was possible for him not to sin, but he did sin. For Jesus it was not possible to sin, but that does not mean his temptations were like water off a duck's back. We do not find him resisting the devil by saying, 'You must be joking, I'm the Son of God and therefore impeccable, don't you know?' 

Jesus 'suffered when tempted' (Hebrews 2:18), combatting the evil one by wielding the sword of the Spirit (Matthew 4:4). While Satan sought to tempt Christ by appealing to his unique divine identity, 'if you are the Son of God...' (Matthew 4:3, 5), Jesus responded as one who had 'taken the form of a servant, being born in the likeness of men' saying, 'Man shall not live by bread alone...', (Matthew 4:4). The incarnate Son 'learned obedience through what he suffered' (Hebrews 5:8) in the arena of temptation. Satan did did his worst, but 'full of the Holy Spirit' (Luke 4:1), and in humble dependence on the Father, Jesus vanquished the foe. As Hebrews insists, in Jesus our great High Priest we have 'one who was tempted in all points as we are, yet without sin'. (Hebrews 4:15). Kevin Vanhoozer reflects,

There is no necessary contradiction between Jesus being "open" to temptation and the certainty of never sinning. The temptation was no sham, for it is precisely because Jesus resisted temptation that he could "feel" its full force. He was impeccable yet subject to real temptation in the way that an invincible army is subject to real attack. (Remythologizing Theology: Divine Action, Passion, and Authorship, Cambridge University Press, 2010, p. 432. 

Could Jesus have sinned? No, but 'because he has himself suffered when tempted, he is able help those who are tempted.' (Hebrews 2:18).