Horizon of theology

Using concepts that go beyond what Jesus says is assuming that Jesus is just a mere man who needed some theologians for help. No, I reject that and I believe he did not use philosophical/theological arguments on purpose. God is where human concepts are all bankrupt.

The doctrine of trinity uses Greek philosophical philosophy to explain the being of God. It says God is one in essence and 3 in persons. Greek philosophy was the spirit of the time, and Christians felt the need to defend their religion by engaging in it.

I believe Jesus explicitly avoided using such language because saying he is "the son of God" is deeper in meaning than any theological term.