Don't Be Scared by the Trinity
The idea of God being both three and one is not a contradiction—it's shorthand for saying two really basic things that help us understand the gospel story:
First, God is three because the Father, the Son, and the Spirit are distinct persons.
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In other words, the Father isn't the Son, and the Son isn't the Spirit, and so forth. (The diagram to the right is a helpful summary.)
This means that we don't pray things like "Father, we thank you for dying on the cross for us" because it wasn't the Father who died on the cross for us. It was the Son, Jesus the Christ, who died on the cross for us.
It also means that we probably shouldn't ask Jesus into our hearts. This is really popular language in the church (and has been for decades, at least), but it's not well-founded in the Bible. The one who lives in us is the Spirit, not Jesus. Jesus is a human who's seated at the right hand of the Father in heaven waiting to come back and finish conquering His enemies and redeeming His people. Jesus is not a body-less spirit, so it'd probably be pretty painful for Him to actually live in our hearts. However, His Spirit (a.k.a., the Holy Spirit) does come and live in us. For those that follow Jesus and trust in Him, the Spirit is always with us, making us new and empowering us to do things we never could before as we become more and more like Jesus. When the earliest Christians said things like "Christ lives in me" this is what they meant. They meant that the Spirit of Christ was continuously empowering them, and if we say anything similar, this is what we should mean.
Second, God is one because the Father, the Son, and the Spirit all have one nature that results in a oneness of desire, purpose, and action.
God is one because there's only one definition of what it means to be God. In other words, the Father, the Son, and the Spirit all share in the same nature—they are all fully God. In the words of the early church, Jesus is "Light from Light, true God from true God." This means that, just like the Father, He's fully and truly God. He is all-knowing, is all-powerful, is perfectly good and beautiful, has always existed, is the Creator of all other things, and so on. The same can be said of the Spirit.
This unity of nature is so tight that all three of them exist in perfect harmony. They're not three gods because they are so unified that they always and only work together. They love each other, serve each other, and glorify each other. They have the same plan for the world and work in such harmony that any time one of them does something, the other two are contributing to it.
(Notice: saying that there's one God doesn't mean that somehow the Father, the Son, and the Spirit are each three parts of the one, true God who alone is fully God. Each of them alone is completely divine.)
Finally, understanding who God is gives us a really effective handle on telling the gospel story.
This may all seem irrelevant, but it's actually very practical because understanding the Trinity goes hand in hand with understanding the grand gospel story. That’s because each of the members of the Trinity plays a vital part in the gospel: The three existed together in perfect harmony before all other things. Then they decided to create. Then humanity rebelled against them and broke creation. So the Father sent the Son into creation to permanently become a part of creation and fix it from the inside out. So the Son died and resurrected, conquering death for the creatures. But their plan was not just to die for the creatures and leave them alone; it was to transform the creatures to be like the Son—to complete the process of redemption. So after His resurrection, the Son appeared to lots of people and then went back to heaven to wait. And while He’s waiting with the Father, they’ve sent the Holy Spirit into creation to begin transforming us creatures. Eventually, when the time is right, the Son will return from heaven and complete the process of redemption by resurrecting us all. And then, victory of victories, glory of glories, heaven and earth will be united so that we creatures who have been made gloriously like the Son will live together forever in the presence of the Son, and the Spirit, and the Father.
Praise be to God! Praise the Father, praise the Spirit, praise the Son! Praise their working together with overwhelming patience and grace to bring the world to a beautiful climax.
We don't have Jesus now, but we have His Spirit—let Him take you into the presence of the Father in prayer!
Sometimes I think the earliest church had it easiest because they got to see Jesus and we haven't yet. But Jesus says that it's better for the church for Him to be away and for the Spirit to be here. Do we believe that?
The great thing about the harmony of the Trinity is the access we now have to God. It's the Spirit that comes and lives in us and empowers us to pray powerfully. He unites us to Jesus who lives in the very presence of the Father, right now. So when we pray, what's really happening is that by the Spirit, we're in the Son, and therefore in the very presence of the Father. When we pray, He listens because it's His beloved Son, Jesus, that's praying for us. If this isn't good news, I'm not sure what is.
For more information, listen to one of our recent sermons where I expanded on this idea in the context of Acts chapter 2 where we see the growth of the earliest church: click here to listen.