The Catholic and mainstream Protestant (and to some extent Eastern and Oriental Orthodox) gospel usually presented is that you must believe in Trinity doctrine to be a Christian and be saved. That is not the gospel preached by Paul. It contradicts what Paul preached. It is accursed.
Galatians 1:8-9 “But even if we or an angel from heaven should preach a gospel contrary to the one we preached to you, let him be under a curse! As we have said before, so now I say again: If anyone is preaching to you a gospel contrary to the one you received, let him be under a curse!”
If the Trinity doctrine is essential, the question is then, why did Jesus not reveal it to his apostles, and why it did not matter that they did not know it.
Many young people less than sixteen years old today have the Holy Spirit clearly manifested in them, as made known in their contributions in worship service meetings, and live lives showing their true discipleship, yet at their age they could not possibly understand Trinitarian core concepts such as homoousiou, and coeternal consubstantial co-equality, so they cannot be said to believe in the Trinity.
All this proves that the true gospel as preached by Apostle Paul cannot include belief in the doctrines of Trinity.
