For non-Christians (and Christians I suppose), the divinity of Jesus (Yeshua, Son of God, etc) was established by the Council of Nicea under the Roman ruler, Constantine c. 320. That such a person existed seems pretty sure; the attributes he may or may not have had are up for grabs. Someone from the House of David was crucified (otherwise why the written sign, 'King of the Jews'?). There are excellent books that delve into the mystery (Holy Blood, Holy Grail; The Messianic Legacy). It seems fairly certain that such a person existed. However, what position he holds in the grand scheme of things is in the air for lots of people.