Here I copy a discussion that I had with a visitor of these pages, in case more are interested:
Q. As a messenger for our Biblical study group, your past clarifications have been of great benefit. At the present time our enigma is the following and we ask for your clarification: You have advised us that Plato’s Timaeus references God’s progeny, humanity, as γέννημα. Isaiah 7:14 uses the word υἱὸν for son. We wish to know its context.
A. I'm not sure I understand. What is precisely your question or doubts about Isaiah 7.14 and Timeaus?
Q. Isaiah 7:14, “Behold a virgin shall bear a son, and shall call his name Immanuel.” Our original source advised that the word υἱὸν originates from Plato’s Timaeus. You advised us otherwise, that Timaeus uses the word γέννημα, meaning progeny and not υἱόν. Our question is, what is the source and meaning of υἱόν? Our Greek-English dictionary does not show such a word, and its modern interpretation for son is γιος.
Α. Let me first suggest that you keep some distance from purely lexicographical research. A careful reading of Timaeus, to realize the context of the use of words, would let you avoid the trap of 'yios' and 'son'.
Plato doesn't use in Timaeus the word "son" -- but he calls the Creator of the world "Creator and Father" (ποιητὴν καὶ πατέρα - cf Timaeus 28c). Since he is a father, he must have a son -- or a daughter, but progeny may also refer to a work that bares a perfect resemblance of its maker.
In any case Plato tries to emphasize the being of the world as the being of a living creature and an image of the Creator so close to Him, that we can not refer to the creation of the world as if it were a 'construction', since this creation is closer to giving birth.
Q. Are we to understand that Isaiah 7:14 use of υἱόν can also be interpreted as, “a living entity and an image of the Creator so close to Him?” Is it possible that the word υἱόν also may refer to “a progeny [humanity] that bares a perfect resemblance of its maker,” i.e. “Immanuel, God is with us?”
A. Isaiah 7, 14 refers specifically to a human being, to a son, not to a vague "living entity". As a son, he has the nature of his mother, the virgin, and of his father, God. Isaiah 7, 14 refers to Christ, according to the interpretation of the Church, but in any case it refers to a godly child born to a Virgin and God himself.