I am sure that many of you aware that in John 1:1, in the original Greek, when the text states, "And the Word was God," there is no defitine article before the word "God" (theos) but in the same verse there is a definite article before the word "God" when it refers to God the Father. Now some Jehovah's witnesses will argue that the passage should then be translated "The Word was a god". How does a Trinitarian Christian answer this?
It is a possible translation. The sentence is grammatically ambiguous. The best way to differentiate in strictly scientific terms is to compare with the earliest translations to know what the understanding of its contemporaries was.
In the Vulgat we have:
In principio erat Verbum,
et Verbum erat apud Deum,
et Deus erat Verbum.
In the Vetus Latina we have:
1 In principio erat
uerbum et uerbum erat apud
et ds̅ erat uerbum
As poor as my Latin is, it seems to me that the Latin translations evidence that the common understanding of the sentence is that "The Word was God." I say that because in Portuguese, which is a Latin-derived language, what we have is "o Verbo era Deus" which seems close enough and would translate into English in the traditional way.
Another way to distinguish it, is to see how commentators interpreted it, as meaning (a) or (b). Let's see:
HILARY; You will say, that a word is the sound of the voice, the enunciation of a thing, the expression of a thought: this Word was in the beginning with God, because the utterance of thought is eternal, when He who thinks is eternal. But how was that in the beginning, which exists no time either before, or after, I doubt even whether in time at all? For speech is neither in existence before one speaks, nor after; in the very act of speaking it vanishes; for by the time a speech is ended, that from which it began does not exist. But even if the first sentence, in the beginning was the Word, was through your inattention lost upon you, why dispute you about the next; and the Word was with God? Did you hear it said, “In God,” so that you should understand this Word to be only the expression of hidden thoughts? Or did John say with by mistake, and was not aware of the distinction between being in, and being with, when he said, that what was in the beginning, was not in God, but with God? Hear then the nature and name of the Word; and the Word was God. No more then of the sound of the voice, of the expression of the thought. The Word here is a Substance, not a sound; a Nature, not an expression; God, not a nonentity.
HILARY; But the title is absolute, and free from the offense of an extraneous subject. To Moses it is said, I have given you for a god to Pharaoh: but is not the reason for the name added, when it is said, to Pharaoh? Moses is given for a god to Pharaoh, when he is feared, when he is entreated, when he punishes, when he heals. And it is one thing to be given for a God, another thing to be God. I remember too another application of the name in the Psalms, I have said, you are gods. But there too it is implied that the title was but bestowed; and the introduction of, I said, makes it rather the phrase of the Speaker, than the name of the thing. But when I hear the Word was God, I not only hear the Word said to be, but perceive It proved to be, God.
BASIL; Thus cutting off the cavils of blasphemers, and those who ask what the Word is, he replies, and the Word was God.
THEOPHYL. Or combine it thus: From the Word being with God, it follows plainly that there are two Persons. But these two are of one Nature; and therefore it proceeds, In the Word was God: to show that Father and Son are of One Nature, being of One Godhead.
ORIGEN; We must add too, that the Word illuminates the Prophets with Divine wisdom, in that He comes to them; but that with God He ever is, because He is God. For which reason he placed and the Word was with God, before and the Word was God.
CHRYS. Not asserting, as Plato does, one to be intelligence, the other soul; for the Divine Nature is very different from this... But you say, the Father is called God with the addition of the article, the Son without it. What say you then, when the Apostle writes, The great God and our Savior Jesus Christ; and again, Who is over all, God; and Grace be unto you and peace from God our Father; without the article? Besides, too, it were superfluous here, to affix what had been affixed just before. So that it does not follow, though the article is not affixed to the Son, that He is therefore an inferior God.
So, from translation and comments, which are interpretations after all, we know which of the senses in that ambiguous sense is the traditional one.