What is the Trinity? The Three-in-One explained

Explaining the trinity is hard because of God’s transcendent nature. However, the doctrine is both rational and logical and we explore this here.

Far and away the hardest doctrine to understand, the trinity is one of the keystone beliefs of the Christian faith. It is really hard to talk about it without unintentionally speaking heresy, so in this article we will present the basic doctrine and then explain why it make philosophical and logical sense to be that way.

Doctrine of the Trinity

According to the Catechism, here is what we understand the Trinity to be:

  • There is only one God
  • God is 3 co-existing eternal persons, none of whom are the others
  • Each person of the trinity is fully God

Explaining the trinity

Objections to this

  • If there is only one God, then only one being can be God. Three persons would result in three Gods
  • If each member of the Trinity is not the others, but each is fully God, then this does not make logical sense.
  • Either: each is only a third of God, only one of the Trinity is God, or they are just different personalities of one God and not distinct persons.

Problem with these objections

  • Our source for the Trinity’s doctrine is divine revelation, especially through the person of Jesus Christ. It needs to be this because we have no way of empirically testing something in a higher dimension to us. Therefore, our only source for understanding God’s nature is God himself.
  • He explains about Himself in scripture (John 1:14, John 10:30, Luke 1:35, Matthew 3:16-17, 1 John 5:7-8 etc) and always refers to Himself in plural (Gen 1:26-27). What scripture teaches is the doctrine stated above. Therefore, the biggest and most important objection is “does the Trinity make logical sense”.

How does 3 persons in 1 being make logical sense

  • In his book Mere Christianity, C S Lewis tackles this question by using a cube as an analogy. While in our 3D perspective we can fully comprehend how it looks, in a 2D universe we would not.
  • In a 2D universe we would be able to comprehend a square easily because we’d see its length and width but would have no way of perceiving its volume. Every time you would look at it from a different side or angle all you would ever see is more 2D shapes.
  • With each additional dimension you add, a deeper reality and complexity is added to a creation.
  • As Christians, we believe that God is transcendent of our own dimension of time and space, and that the divine level is the highest dimension. For this reason, just like how a cube gains complexity by being made up of 6 squares, on the divine level a single being is no longer a single person but rather can be made up of 3 persons instead.

Explaining the trinity

How is 3 persons in 1 being philosophically rational

  • With the divine level being the highest reality, we understand God’s qualities to be greater than our own in every way. While man can be powerful, God is all powerful (Job 37:23). While man can be knowledgeable, God is all knowing (Psalm 147:5). Even though we can be good, God is always good and selflessly loves (John 3:16). In this way, it follows that while we as people are singular in our person-hood (unitarian), God is multi-personal.
  • If He was not, and limited to being unitarian, He would not be greater in all ways to the human person. This would contradict what we have learned of Him in scripture (Psalm 113:4-6, Job 26:14, Isaiah 55:8–9, Psalm 8:3–4).
  • Additionally, as we know God is all loving (Deuteronomy 7:9, Psalm 136:26) it would make sense that God is multi-personal. We know that in the beginning there was only God (Genesis 1). If God is always loving, however, how could He have been so if He was unitarian? A unitarian God would be unable to be all loving because in the beginning if there was only God, who would He be loving?
  • God does not change (Malachi 3:6) so, from a philosophical point of view, He would have to be multi-personal to allow Him to be constantly all loving. A multi-personal God could be ever-loving because even when He alone exists, He could still be showing love within His three persons.

Follow on objection

  • If we go with the logic that God must be multi-personal to be both all-loving and greater than humankind in every way, why are we then limiting God to only being three persons? With this logic God could surely be 1,000s of persons.

Answering this objection

  • Yes, logically this could be possible. God could in theory choose to be any infinite number of persons. However, quantity by itself does not make someone greater. While God could choose to be as many persons as He wanted, it is not the number of persons He is that makes Him greater.
  • What makes God greater is the ability to be multi-personal over the restriction to only be one person. It is not about quantity but rather that He has the ability.
  • We claim that God has three persons because that is what God has revealed to us through scripture and tradition. While it is entirely possible that God could have more, the three we know are what he has revealed to us in scripture (Matthew 28:19). To the best of our knowledge, God has chosen to be three persons. His reasons are his own and, while we could attempt to guess them, we would be trying to attach human understanding to a being whose reasoning is infinitely greater than our own.

Explaining the trinity


  • The doctrine of the Trinity is made unfathomable by its transcendent nature.
  • This doesn’t mean, however, that it is illogical. Both from a logical and philosophical standpoint, God being Trinitarian is entirely rational.
  • Ultimately, the objections are attempts by us to make up a god that we can understand rather than be faced with the being presented in scripture which is beyond our mental capacity to understand. If God was fake, then we would surely make up one that we could understand.
  • A great exercise to realise your own mental capacity is to try and think of a completely new colour. We know they exist, and that many birds and sea creatures see thousands more colours, but because our eyes have never seen them first hand, we can’t mentally grasp what they would even look like.
  • The complexity of the Trinity is, in many ways , an affirmation of God’s divinity and validity. It adds credence to His divinity because it shows how His transcendent nature is so extremely different and complex compared with our own. It adds credence to the claim of God’s existence because, whereas our imagination is ever limited to things we know, the doctrine of the Trinity is completely beyond our ability to properly understand, let alone make up!

“Wherever there is love, there is the Trinity: a lover, a beloved, and a fountain of love”

St Augustine (AD 354-430)