No man hath seen God at any time; the only begotten Son, which is in the bosom of the Father, he hath declared him. (KJV)
1. As it is written in the KJV, there is no Trinitarian inference in the verse.
2. There are versions such as the NIV and NASB, however, that are translated from a different textual family than the King James Version, and they read “God” instead of “Son.”
NIV: “No one has ever seen God, but God the One and Only, who is at the Father’s side, has made him known.”
NASB: “No man has seen God at any time; the only begotten God, who is in the bosom of the Father, He has explained Him.”
The NIV and NASB represent theologians who believe that the original text read “ho monogenes theos” = “the unique, or only begotten God,” while the KJV is representative of theologians who believe that the original text was “ho monogenes huios” = “the only begotten Son.” The Greek texts vary, but there are good reasons for believing that the original reading is represented in versions such as the KJV. Although it is true that the earliest Greek manuscripts contain the reading “theos,” every one of those texts is of the Alexandrian text type. Virtually every other reading of the other textual traditions, including the Western, Byzantine, Caesarean and secondary Alexandrian texts, read huios, “Son.” The two famous textual scholars, Westcott and Hort, known for their defense of the Alexandrian text type, consider John 1:18 to be one of the few places in the New Testament where it is not correct.
A large number of the Church Fathers, such as Irenaeus, Clement and Tertullian, quoted the verse with “Son,” and not “God.” This is especially weighty when one considers that Tertullian argued aggressively for the incarnation and is credited with being the one who developed the concept of “one God in three persons.” If Tertullian had had a text that read “God” in John 1:18, he certainly would have quoted it, but instead he always quoted texts that read “Son.”
It is difficult to conceive of what “only begotten God” would have meant in the Jewish culture. There is no use of the phrase anywhere else in the Bible. In contrast, the phrase “only begotten Son” is used three other times by John (3:16 and 18; 1 John 4:9 – KJV). To a Jew, any reference to a “unique God” would have usually referred to the Father. Although the Jews of John’s day would have had a problem with “only begotten God,” Christians of the second century and beyond, with their increasingly paradoxical understanding of Christology and the nature of God, would have been much more easily able to accept such a doctrine.
The reason that the text was changed from “Son” to “God” was to provide “extra evidence” for the existence of the Trinity. By the second century, an intense debate about whether or not Jesus was God raged in Alexandria, Egypt, the place where all the texts that read “God” originated. The stakes were high in these debates, and excommunication, banishment or worse could be the lot of the “loser.” Changing a text or two to in order to “help” in a debate was a tactic proven to have occurred. An examination of all the evidence shows that it is probable that “the only begotten son” is the original reading of John 1:18. For a much more detailed accounting of why the word “Son” should be favored over the word “God,” see The Orthodox Corruption of Scripture, by Bart Ehrman (Oxford University Press, New York, 1993, pp. 78-82).
3. Even if the original text reads “God” and not “Son,” that still does not prove the Trinity. The word “God” has a wider application in Hebrew, Aramaic and Greek than it does in English. It can be used of men who have divine authority (See John 10:33 and Heb. 1:8). There is no “Trinitarian Formula” in this verse that forces a Trinitarian interpretation.