Facts can be difficult things

In the beginning was the Word, and the Word was with God, and the Word was God. [....] And the Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth. (John 1:1, 14, ESV)

Gayle Trotter writing at Evangel responds to a friend who has objections to the doctrine of the Trinity.

As my friend rightly noted, the Bible nowhere contains the word “Trinity.” An easy response, though, is that many bedrock Christian doctrines are given names that are not found in the Bible, such as “monotheism,” “incarnation,” or “divinity.” ....

After describing how the Church came to define the doctrine, and discussing the issue of subordination in the relationship of Father, Son and Holy Spirit, Trotter comes to her friend's last objection:

.... How do you reconcile Old Testament monotheism with a triune God?

We must frequently hold two principles in tension. Two opposing heresies lie on either side of orthodox Trinitarian doctrine. The first heresy, Modalism, claims that there are three terms for the same God, and the only difference is where this God appears and at what time. The second heresy, Tritheism, asserts that there are three equal, independent and self-sufficient beings who are all divine. Both of these heresies are quite a bit simpler and easier to grasp than the Trinity, but each one lacks an essential element (three persons in the case of Modalism; one God in the case of Tritheism). ....

.... As [C.S.] Lewis observed, “If Christianity were something we were making up, of course we could make it easier. But it is not. We cannot compete, in simplicity, with people who are inventing religions. How could we? We are dealing with Fact. Of course anyone can be simple if he has no facts to bother about.” .... (more)

The Trinity: 3-D Divine Mystery » Evangel | A First Things Blog