Admittedly, the Trinity is an interesting theory and it certainly quelled some of the early Church's division on the nature of God, but it is just that – a theory.Many conservative Christians believe perhaps some of what Sandlin says above. They think that while the Trinity is a concept that helps theologians overcome certain obstacles in reconciling some snippets of scripture, it is more esoteric and "head knowledge" than the central message of the gospel, which is the message we should truly be sharing.
…I'm not saying the theory of Trinity is wrong. I'm just not saying it's definitively right, which is exactly what many of its adherents do when they say that if you don't believe in the Trinity, you can't be Christian.
Here's the thing, if the Trinity is that important, doesn't it seem like Jesus or the book of Acts or Paul or James or Peter or John would have talked more directly about it?
The lack of biblical witness leaves me to believe that either there simply was no understanding of a Trinitarian God at the time books of the Bible were written, or that the concept was so unimportant to their faith that it mostly wasn't mentioned.
So, why do we make it so important?1
If you believe something like this, may I tell you in the kindest way possible that you are completely wrong? Because you are. As Dr. Fred Sanders wrote in his compelling book The Deep Things of God: How the Trinity Changes Everything, "the doctrine of the Trinity inherently belongs to the gospel itself."2 Let's look at some aspects of the work of Christ's atonement on the cross to see just how dependent it is on the concept of the Trinity.
The Trinity Demonstrates God's Sacrifice is the GreatestThe Trinity is necessary for understanding the total sacrifice of Christ for our sins. Paul in Romans 5 puts it this way:
For one will scarcely die for a righteous person—though perhaps for a good person one would dare even to die—but God shows his love for us in that while we were still sinners, Christ died for us. Since, therefore, we have now been justified by his blood, much more shall we be saved by him from the wrath of God. For if while we were enemies we were reconciled to God by the death of his Son, much more, now that we are reconciled, shall we be saved by his life.3Notice how Paul makes a distinction in the passage above with the words God and Christ. He argues that a person giving up his own life for a righteous man would be a great sacrifice; it would mean more that a person gave up his life for an unrighteous man. However, we have been "reconciled to God by the death of His Son." It's one thing to lay down one's own life, which Jesus did in following the will of the Father. It's a completely different level of sacrifice to lay down the life of your beloved son for the sake of an enemy! Without the concept of the Trinity, this level of sacrifice is missed.
The Trinity Allows Jesus to Atone for All HumanityJesus' offering of Himself to the Father reconciles us to God. But only the blood of the second person of the Trinity could possibly atone for the sins of all humanity. Anything less wouldn't have a universal effect. Romans 8:3-4 is very clear here: "For God has done what the law, weakened by the flesh, could not do. By sending his own Son in the likeness of sinful flesh and for sin, he condemned sin in the flesh, in order that the righteous requirement of the law might be fulfilled in us, who walk not according to the flesh but according to the Spirit." The writer to the Hebrews completes the thought:
But when Christ appeared as a high priest of the good things that have come, then through the greater and more perfect tent (not made with hands, that is, not of this creation) he entered once for all into the holy places, not by means of the blood of goats and calves but by means of his own blood, thus securing an eternal redemption. For if the blood of goats and bulls, and the sprinkling of defiled persons with the ashes of a heifer, sanctify for the purification of the flesh, how much more will the blood of Christ, who through the eternal Spirit offered himself without blemish to God, purify our conscience from dead works to serve the living God.Jesus needed to appear in the heavenly realms, in the true Holy of Holies to atone for sinful humanity. He couldn't be just a man, as a righteous man might be able to pay for the sins of an unrighteous man, but Jesus paid for the sins of all flesh.
…So Christ, having been offered once to bear the sins of many, will appear a second time, not to deal with sin but to save those who are eagerly waiting for him.
The Trinity Makes Resurrection PossibleThe atonement is not the full Gospel. Any presentation of the Gospel message must not stop at Christ's death, but also include His resurrection. We know that without the resurrection of the dead, "you are still in your sins."4 Jesus said that his resurrection was his own to do,5 and Paul tells us that our future resurrection from the dead depends on God's Holy Spirit, who also raised Jesus: "If the Spirit of him who raised Jesus from the dead dwells in you, he who raised Christ Jesus from the dead will also give life to your mortal bodies through his Spirit who dwells in you."6 Thus, without the Trinity, there would be no resurrection and no hope for us. We would be "of all people the most pitied."
The Trinity is necessary for the gospel. One cannot be separated from the other. Sanders sums it up nicely in his book:
Nothing we do as evangelicals makes sense if it is divorced from a strong experiential and doctrinal grasp of the coordinated work of Jesus and the Spirit, worked out against the horizon of the Father's love. Personal evangelism, conversational prayer, devotional Bible study, authoritative preaching, world missions, and assurance of salvation all presuppose that life in the gospel is life in communion with the Trinity. Forget the Trinity and you forget why we do what we do; you forget who we are as gospel Christians; you forget how we got to be like we are.7
References1.Sandlin, Mark. "No Trinity For Me, Please." Patheos. Patheos, 20 Aug. 2014. Web. 04 Sept. 2014. http://www.patheos.com/blogs/thegodarticle/2014/08/no-trinity-for-me-please.
2.Sanders, Fred. The Deep Things of God: How the Trinity Changes Everything. Wheaton, Ill.: Crossway, Kindle Edition, 2010. 9.
3. Romans 5:7-10,ESV Study Bible: English Standard Version. Wheaton, Ill: Crossway Bibles, 2007. Print.
4. 1 Cor. 15:17.
5. John 2:21, John 10:18
6. Romans 8:11
7. Sanders, Ibid.