The doctrine of the Trinity is easy to state but difficult to explain, and impossible for mortal minds to fully grasp. In its most basic form (like describing the speed of light as really, really fast), the Trinity doctrine means there is one God who eternally exists as three distinct Persons — the Father, Son, and the Holy Spirit. The Trinity doctrine affirms that God is three, yet one.
The Trinity—the teaching that there is one God, and that the Father, the Son, and Holy Spirit are distinct Persons yet each fully God—is unique to Christianity. Other religions have multiple gods, father and son deities, and resurrected deities, but only Christians hold there is but one God, and that He has revealed Himself as three Persons.
Some have cheapened the reality of the Trinity by suggesting the Father, Son, and Spirit have shared goals or purpose—that is true, but there is more.
Others have tried to explain the triune nature of God by pointing to water, and how its molecular composition remains the same as it takes different forms (liquid, ice, vapor). But though the molecular composition of water in the deepest ocean is the same as the water atop the highest mountains, it is not the same water. And that’s what makes the Trinity doctrine unique. Each Person in the Trinity is distinct from the others (just as water in China is distinct from ice in Alaska), and yet, at the same time, each Person shares the same nature and essence as the others in the Trinity. This is how Jesus could say to Philip, “Don’t you know me, Philip, even after I have been among you such a long time? Anyone who has seen me has seen the Father…” (John 14:9). This is why John 1:1 states that Jesus is the Word and that the “Word was with God and that the Word was God” (John 1:1). This is why Peter told Ananias that he “lied to the Spirit” (Acts 5:3) and one verse later, said that he had “lied…to God” (Acts 5:4). This is how God is the Creator in Genesis 1, and Jesus is the Creator in John 1:3 and Colossians 1:16.
The Trinity doctrine is deep and mysterious, but it is a foundational component of the Christian faith. Without the Trinity doctrine, the promises and work of Jesus would fall short—he could be a great teacher but could not be the “Great Shepherd” and Redeemer. According to Scripture, we must believe there is just one God, and Jesus is Emmanual, “God with us.”
Links to two files to aid your understanding of the Trinity doctrine follow: