“If there were no trinity, there could be no incarnation, no objective redemption, and therefore no salvation; for there would then be no one capable of acting as Mediator between God and man. In his fallen condition man has neither the inclination nor the ability to redeem himself. All merely human works are defective and incapable of redeeming a single soul.
Between the Holy God and sinful man there is an infinite gulf; and only through One who is Deity, who takes man’s nature upon Himself and suffers and dies in his stead, thus giving infinite value and dignity to that suffering and death, can man’s debt be paid. Nor could a Holy Spirit who comes short of Deity apply that redemption to human souls. Hence if salvation is to be had at all it must be of divine origin.
If God were only unity, but not plurality, He might be our judge, but, so far as we can see, could not be our Saviour and sanctifier. The fact of the matter is that God is the way back to Himself, and that all of the hopes of our fallen race are centred in the truth of the Trinity.”
Loraine Boettner (2011-10-19). The Trinity (Kindle Locations 1110-1117). Kindle Edition.