When Jesus began His earthly ministry, He was baptised by John the Baptist in the river Jordan. The account reads this way...
And when Jesus was baptized, immediately he went up from the water, and behold, the heavens were opened to him, and he saw the Spirit of God descending like a dove and coming to rest on him; and behold, a voice from heaven said, “This is my beloved Son, with whom I am well pleased.” (Matthew 3:16-17)
In this passage we hear God (“the Father”) referring to Jesus as His “beloved Son”, and we also see the Spirit of God descend on Him. There are three persons... the Father, the Son, and the Spirit of God, often referred to as the Holy Spirit elsewhere in Scripture. Yet each of these three (clearly separate) persons are all, in fact, God. We know this when we consider all that Scripture has to say about each of these three persons. The Holy Spirit, for example, was involved in Creation:
In the beginning, God created the heavens and the earth. The earth was without form and void, and darkness was over the face of the deep. And the Spirit of God was hovering over the face of the waters. (Genesis 1:1-2)
Jesus Christ was also actively involved in the Creation:
For by him [the Son, see v13] all things were created, in heaven and on earth, visible and invisible, whether thrones or dominions or rulers or authorities—all things were created through him and for him. (Colossians 1:16)
The Holy Spirit inspired the writers of Scripture to write the very Words of God:
For no prophecy was ever produced by the will of man, but men spoke from God as they were carried along by the Holy Spirit. (2 Peter 1:21)
But we see that this same Spirit is also called the “Spirit of Christ”...
Concerning this salvation, the prophets who prophesied about the grace that was to be yours searched and inquired carefully, inquiring what person or time the Spirit of Christ in them was indicating when he predicted the sufferings of Christ
and the subsequent glories. (1 Peter 1:10-11)
Each member of the Trinity participates in the works of God, and each member shares all of the attributes of God.
From the very beginning, God said “Let us make man in our image” (Genesis 1:26), indicating a plurality of persons in the Godhead. The Bible tells us that “God is love” (1 John 4:8). That is to say, one of God's essential characteristics is love. This characteristic has always been true of God, even before He created mankind. But love can only exist between persons. Before God had created any persons, how was He able to love? You see, the Trinity is essential to the Bible's claim that God is love. God's characteristic of love was exercised throughout all eternity between the three members of the Trinity. You cannot have an eternally loving God unless you have a plurality of persons in the Godhead, having co-existed eternally.
It is beyond our ability, being limited mortal beings, to comprehend the Trinity. Many analogies have been put forth... perhaps we can think of a man who is a “husband”, a “father” and a “son” all at the same time. But this is not sufficient in describing the Trinity, because this is just one man in three roles, and not three distinct persons. Or perhaps the Trinity is like water having three states; solid, liquid and gas. But a body of water is not all of these at the same time. Some have seen the Trinity as different “modes” of God's existence, much like the water illustration. They would say that God the Father ceased to exist when God became incarnate as the Son. And then the Son ceased to exist when He ascended to heaven and became the Holy Spirit. But we've already seen that this is false, as all three were clearly seen to coexist at the same time on the occasion of Jesus' baptism (see passage above, Matthew 3:16-17). The truth is that there is no analogy we can make to describe this spiritual reality. It is a mystery of God.
Tomorrow I'll spend some time on another perplexing mystery of God; the sovereignty of God and the responsibility of man. Until then...
I and the Father are one. (John 10:30)