"For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one." -1 John 5:7 (KJV)
This verse may be the most controversial one in the entire Bible. It is said that no Greek manuscripts prior to the 16th or even 17th century contained anything past "For there are three that bear record in heaven," and that the original manuscripts did not contain the explicit reference to the Trinity. It is also very often used by atheists and Muslims to discredit the Bible. To support this idea, I've heard asked, "Why was this verse not used early on when the conflict concerning the nature of Christ was full-blown?"
So I ask:
a.) Was this verse used to defend the divinity of Christ during St. Athanasius' time?
b.) Are there translations of the Bible prior to the 16th century that contained the full reference to the Trinity?
c.) How would a confusion like this arise in the first place? If it were originally there, there should be no credible assertion that it wasn't. If it was not originally there, then there should have been some publicity and resistance when it was inserted. So how would this happen?