I understand the word theos may be translated as "God" or as "god." Bible writers added words (the, true, only or one) to indicate the Almighty. The Nicene Creed describes the Father as "one theos" and the Son as "true theos from true theos." Is there anything in the Greek of this phrase to indicate whether this should read "God" or "god?"
To be fair, I don't know if a pedantic, strict literal word-for-word translation supports this answer. However, it is hardly unreasonable to consider the overall content of what is being translated.
In that respect, where the first part of the Creed desires to teach the truth and uniqueness of that which we worship, it is right that we should use "God" and not "[a] god". It follows then that the second part, teaching that Jesus Christ is "of one substance with the Father" — that He is God — would also rightly use "God" and not "god".
We can go further, however, and also look at the context in which the creed was written. Astute observers will have no doubt noted that this answer is Trinitarian in perspective, and very astute observers will note I have deleted the prior disclaimer to that effect. The reason for doing so is that this answer is written, as is appropriate, in consideration of the views of the authors of the document in question.
Condemnation of Arianism was a major theme of the Council of Nicea (which produced the eponymous creed); thus, while we might argue about whether or not the authors succeeded (via the textual context) in their intent of clearly elucidating that Christ is God (with a capital 'G'), or even whether such view is correct from a biblical standpoint, it is abundantly clear from the historical context that that was the intent of the authors. From that perspective, we can give a definitive answer, since addressing the question from a perspective different from that of the original authors is to dishonestly discard the intent of said authors.
Should the phrase "true God from true God" in the Nicene Creed be translated as "true god from true god"?
The short answer is no, at least from a Triniarian point of view, which accounts for the the vast, vast majority of Christians. The Council of Nicea (325) and the Council of Constantinople (381) were Trinitarian in their very essence!!! If the Council Father could have used upper case letters as we do in modern English, I am 100% positive they would have in order to emphasize their meaning within the Creeds themselves.
The phrases in question must be see as a complete part of the second paragraph of the Nicene Creed In order to understand the translation involved.
I believe in one Lord Jesus Christ, the Only Begotten Son of God, born of the Father before all ages. God from God, Light from Light, true God from true God, begotten, not made, consubstantial with the Father; through him all things were made. For us men and for our salvation he came down from heaven.
The Second Person of the Blessed Trinity is the Word of God, the Son. This Word of God, Jesus Christ, proceeds from the Father. He was “born” and “begotten” but not made. This is a mystery that is very difficult to understand. Much ink has been spilled in theology on how Jesus can be both God and man.
In other words, Jesus is fully God and He is eternal, just as the Father is eternal. This paragraph emphasizes that there is one God but the Father is nonetheless distinct as a Person from the Person of the Son.
The Council Fathers went to great length to combat the Arian heresy which claimed that Jesus was created and was not truly God. We believe that Jesus is fully God and fully man. As the Word of God, He was existed forever and will always exist. He proceeds from the Father as God from God and Light from Light, true God from true God.
There is also the realization that it is through the Word of God that all things were made. God reveals to us in Genesis God speaks in order to create. He says, “Let there be light.” And there was light. Jesus Christ, the Word of God, was sent on a mission by the Father to come down from heaven in order to redeem humanity and offer us salvation.
Since the original Greek does not use upper class and lower case letter, the nuance of what the Church Council Fathers could not grammatically express the differences as in modern English along side their theological thoughts in written form. Besides, the English translation did not come about for centuries later and again was done in a Trinitarian expression of their faith in the Sacred Trinity. This is obviously seen in the Nicene Creed itself: Et unam, sanctam, cathólicam et apostólicam Ecclésiam, of the Nicene Creed.
And I believe one holy Catholic and Apostolic Church; I acknowledge one Baptism for the remission of sins; and I look for the resurrection of the dead, and the life of the world to come. Amen. - English versions of the Nicene Creed
For convenience I am including the Nicene Creed in the original Greek text, as well as a Latin and English translation. Let be upfront about the texts being involved here:
Πιστεύομεν εἰς ἕνα Θεὸν Πατέρα παντοκράτορα πάντων ὁρατῶν τε καὶ ἀοράτων ποιητήν· καὶ εἰς ἕνα Κύριον Ἰησοῦν Χριστὸν τὸν Υἱὸν τοῦ Θεοῦ, γεννηθέντα ἐκ τοῦ Πατρὸς μονογενῆ τουτέστιν ἐκ τῆς οὐσίας τοῦ Πατρος Θεὸν ἐκ Θεοῦ, Φῶς ἐκ Φωτός, Θεὸν ἀληθινὸν ἐκ Θεοῦ ἀληθινοῦ, γεννηθέντα, οὐ ποιηθέντα, ὁμοούσιον τῷ Πατρί, δι’ οὗ τὰ πάντα ἐγένετο τά τε ἐν τῷ οὐρανῷ καὶ τὰ ἐν τῇ γῇ, τὸν δι’ ἡμᾶς τοὺς ἀνθρώπους, καὶ διὰ τὴν ἡμετέραν σωτηρίαν, κατελθόντα, καὶ σαρκωθέντα, καὶ ἐνανθρωπήσαντα, παθόντα, καὶ ἀναστάντα τῇ τρίτῃ ἡμέρᾳ, ἀνελθόντα εἰς τοὺς οὐρανούς, ἐρχόμενον κρῖναι ζῶντας καὶ νεκρούς. καὶ εἰς τὸ Ἅγιον Πνεῦμα. Τοὺς δὲ λέγοντας Ἦν ποτε ὅτε οὐκ ἦν, καὶ Πρὶν γεννηθῆναι οὐκ ἦν, καὶ ὅτι Ἐξ οὐκ ὄντων εγένετο, ἢ Ἐξ ἑτέρας ὑποστάσεως ἢ οὐσιάς φάσκοντας εἶναι ἢ κτιστόν ἢ τρεπτόν ἢ ἀλλοιωτὸν τὸν Υἱὸν τοῦ Θεοῦ, τούτους ἀναθεματίζει ἡ ἁγία καθολικὴ καὶ ἀποστολικὴ ἐκκλησία.
Credimus in unum Deum patrem omnipotentem, omnium visibilium et invisibilium factorem. Et in unum Dominum nostrum Jesum Christum filium Dei, natum ex Patre unigenitum, hoc est, de substantia Patris, Deum ex Deo, lumen ex lumine, Deum verum de Deo vero, natum non factum, unius substantiae cum Patre, quod graece dicunt homousion, per quem omnia facta sunt quae in coelo et in terra, qui propter nostram salutem descendit, incarnatus est, et homo factus est, et passus est, et resurrexit tertia die, et adscendit in coelos, venturus judicare vivos et mortuos. Et in Spiritum sanctum. Eos autem, qui dicunt, Erat quando non erat, et ante quam nasceretur non erat, et quod de non exstantibus factus est, vel ex alia substantia aut essentia, dicentes convertibilem et demutabilem Deum: hos anathematizat catholica Ecclesia.
We believe in one God, the Father almighty, maker of all things visible and invisible; And in one Lord, Jesus Christ, the Son of God, begotten from the Father, only-begotten, that is, from the substance of the Father, God from God, light from light, true God from true God, begotten not made, of one substance with the Father, through Whom all things came into being, things in heaven and things on earth, Who because of us men and because of our salvation came down, and became incarnate and became man, and suffered, and rose again on the third day, and ascended to the heavens, and will come to judge the living and dead, And in the Holy Spirit. But as for those who say, There was when He was not, and, Before being born He was not, and that He came into existence out of nothing, or who assert that the Son of God is of a different hypostasis or substance, or created, or is subject to alteration or change, these the Catholic and apostolic Church anathematizes.
One easily understands where the Trinitarian perspective is involved when we read the anathemas at the end of the original Nicene Creed. This was slightly altered by the Council of Constantinople in 381, while maintaining the integrity of the text.