Is it certain that Jesus claimed to be God? Why or why not?
There are verses that hint at it, depending on how you read them, but chances are they have been take out of context. Over the centuries, Jesus has been elevated to godhood status by The Church, and that continues being taught to this day. For every verse that someone quotes that might suggest YES, they are other verses that would contradict them with a big NO.
According to the anonymous authors that actually wrote the NT in Koine Greek, no Jesus never came out and said "I AM GOD." Everything in the NT was written decades after Jesus' death, so it would have been easy to spin the stories to try and make the OT messiah mold conform to the Jesus story. Since it is 3rd party hearsay, be skeptical. Jesus never wrote a single word in the Bible.
John 10:30 "
I and the Father are one."
That verse is often quoted to prove that Jesus does indeed make the claim. However, you have to read the entire chapter in order to understand what Jesus was talking about. By itself it would seem as if Jesus was confirming his deus status, but what does being "one" actually mean? One person? Like minded? Same agenda? Jesus goes on to explain that he was preaching the word of God, and describes the works that he was doing. For that reason, the Jews did not stone him. Obviously he was referring to "being on the same page with God's plan."
John 8:58 "
Truly, truly, I say to you, before Abraham was born, I am."
By itself, that verse does not make a lot of sense in English. It has to do with context and how the phrase was rendered. Many believe that Jesus was referring to himself as God, comparing his answer to
Exodus 3:14 [God said to Moses, I AM WHO I AM; and He said, “Thus you shall say to the sons of Israel, I AM has sent me to you."] However, some scholars argue that Jesus was actually saying something to the effect of "I exist in superior rank to Abraham," and that seems to be supported by
John 8:56 [Your father Abraham rejoiced to see my day, and he saw it and was glad.] Depending on which camp someone is in, they will interpret these verses in a certain way, in order to try and justify a particular belief. The end result of this segment is that Jesus hid in the temple after he said "I am" so that he would not be stoned to death. If he was God, why would he be afraid and need to hide?
Psalm 82:6-7 "I said, “You are gods, And all of you are sons of the Most High.
This supports what Jesus said to the Jews in the temple, when they wanted to stone him. To be called a "god" (with a little 'g') means that you hold a sacred office; that God has chosen you to serve as a judge and representative of His work. It also affirms what Jesus was saying all along...he was a son of God and sent with a purpose. He was human, divinely chosen and doing God's work.