Do you speak on your own authority?
What causes you to speak?
Your brain and it's speech structure known as the broca's area and your mouth utters the words. But your mouth cannot operate and utter words without your brain, right?
God the Father acts as the brain or the seat of authority and the Son acts as mouth of the Father because He is the Word of God. If you can understand spiritually and not naturally as most of mankind do, then you will see the significance in the concept of the Father, Son and Holy Spirit and as to why there are 3 parts to God and yet they remain ONE being!
Furthermore the apostle Paul foresaw this misunderstanding about God centuries ago.
It is written:1 Corinthians 2:14 - But the natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned.
God Bless!