When I mean there must be three Persons in God, I meant that there be must be three because God is real - for three means complete, and God is completely alive - and God is goodness - for three means perfect, and God is holiness itself - and God is one - for three means unity, and the oneness of God is a unity unlike any unity we can possibly imagine.
If there is only one or two Persons in God, than God cannot be thrice-holy, that is, holiness itself, nor can He be an unity, nor can He, while not being holy, real, for God is truly holy. If there is four Persons in God, than God would be worldly, for four means of the world, and if God is worldly, than the heresy of pantheism - that God is everything - would be the truth.
Moreover, if there were not three Persons in God, than God could not be love, for the third Person is the love of God, the living divine love. And since God is love, the third Peson is God, just as the second Person is God and the first Person is God; all three are God, the oneness of God being a unity. God could not simply be an unity in His attributes, either, because than He would have no life in Himself. Even the soul, while being imagination, intellect, and will, has life in itself! So God must have life, and that life is the Holy Trinity.
This is my speculation, of course.