The Stoic philosophers are known for insisting that the Passions be ruled by Reason, and that one should avoid fretting over anything one can't control. What is less well known is that they believed in Ethical Monotheism, or something close to it.
Greek religion, not being based on revelation, did not have clear and precise doctrines about the divine. When a Greek person said "Zeus" they might mean the limited mythological god that appears in Homer (the one who was born at a particular time, squabbled with other deities and had scandalous love affairs) or they might mean the Highest God, who is above all and created everything—what we would call God. Sometimes one and the same document is inconsistent enough to have it both ways; e.g. the Phaenomena of Aratus, which begins by invoking the Zeus who fills all of Nature and provides all blessings, later (with a somewhat embarrassed "if, indeed, the story be true") recounts myths about Zeus being hid in a cave during his childhood!
When St. Paul preached his Sermon on Mars Hill to the Athenians, he could have told them that their religion was completely false and wrong, that Zeus was completely different from the God of Christianity. Instead he chose to begin with those aspects of Greek culture which pointed to the true God.
There have been pious men in all cultures who have realized that there is one highest God, worthy of all worship. And whether they prayed to El or Yahweh or Zeus or Brahman or Allah, he heard them. (If it were forbidden to use the name of pagan deities to refer to Yahweh, then we'd better stop using the term Deity, since Deus is just another form of Zeus. For that matter we'd better stop saying "God", since that term also originally came from pagan worship ceremonies. And we would have to throw out the New Testament as well, since it uses θεος (theos), which was also used for polytheistic gods!) Please note, I am not saying that all religions are the equal or the same; there are many important differences between religions and it matters which one we believe. Yes, the Jews are the Chosen People. But God is not only the god of the Jews, but of the pagans also.
Most glorious of the immortals, invoked by many names, ever all-powerful,
Zeus, the First Cause of Nature, who rules all things with Law,
Hail! It is right for mortals to call upon you,
since from you we have our being, we whose lot it is to be God's image,
we alone of all mortal creatures that live and move upon the earth.
Accordingly, I will praise you with my hymn and ever sing of your might.
The whole universe, spinning around the earth,
goes wherever you lead it and is willingly guided by you.
So great is the servant which you hold in your invincible hands,
your eternal, two-edged, lightning-forked thunderbolt.
By its strokes all the works of nature came to be established,
and with it you guide the universal Word of Reason which moves through all creation,
mingling with the great sun and the small stars.
O God, without you nothing comes to be on earth,
neither in the region of the heavenly poles, nor in the sea,
except what evil men do in their folly.
But you know how to make extraordinary things suitable,
and how to bring order forth from chaos; and even that which is unlovely is lovely to you.
For thus you have joined all things, the good with the bad, into one,
so that the eternal Word of all came to be one.
This Word, however, evil mortals flee, poor wretches;
though they are desirous of good things for their possession,
they neither see nor listen to God's universal Law;
and yet, if they obey it intelligently, they would have the good life.
But they are senselessly driven to one evil after another:
some are eager for fame, no matter how godlessly it is acquired;
others are set on making money without any orderly principles in their lives;
and others are bent on ease and on the pleasures and delights of the body.
They do these foolish things, time and again,
and are swept along, eagerly defeating all they really wish for.
O Zeus, giver of all, shrouded in dark clouds and holding the vivid bright lightning,
rescue men from painful ignorance.
Scatter that ignorance far from their hearts.
and deign to rule all things in justice.
so that, honored in this way, we may render honor to you in return,
and sing your deeds unceasingly, as befits mortals;
for there is no greater glory for men
or for gods than to justly praise the universal Word of Reason.
Cleanthes recognizes that God created the world through his Word, that we are created in his image, that we ought to behave rationally but are foolishly drawn to evil, and that we need for God to intervene to show us the true way, and to save us.
About 250 years later, the Deity heard this prayer and answered it by sending his Word to save us from our sins. The Word had always existed and was the light of the world. But now it entered the world. St. John writes:
In the beginning was the Word,
and the Word was with God,
and the Word was God.
He was with God in the beginning.
All things were created through Him,
and apart from Him not one thing was created
that has been created.
Life was in Him,
and that life was the light of men.
That light shines in the darkness,
yet the darkness did not overcome it.
There was a man named John
who was sent from God.
He came as a witness
to testify about the light,
so that all might believe through him.
He was not the light,
but he came to testify about the light.
The true light, who gives light to everyone,
was coming into the world.
He was in the world,
and the world was created through Him,
yet the world did not recognize Him.
He came to His own,
and His own people did not receive Him.
But to all who did receive Him,
He gave them the right to be children of God,
to those who believe in His name,
who were born,
not of blood,
or of the will of the flesh,
or of the will of man,
but of God.
The Word became flesh
and took up residence among us.
We observed His glory,
the glory as the One and Only Son from the Father,
full of grace and truth.
(John testified concerning Him and exclaimed,
“This was the One of whom I said,
‘The One coming after me has surpassed me,
because He existed before me.’”)
Indeed, we have all received grace after grace
from His fullness,
for the law was given through Moses,
grace and truth came through Jesus Christ.
No one has ever seen God.
The One and Only Son—
the One who is at the Father’s side—
He has revealed Him.
No one has ever came to God, except through his Word; the Word which existed beforehand and gave light to Enoch, Melchizedek, Jethro, Job, Epimenides, Socrates, Plato, Cleanthes, and any of the other pagans who sought after God but who lived before Christ's birth. But now that Jesus has come into the world, we are rescued from ignorance, and we can now place our faith explicitly in a tangible salvation which was revealed to us from Heaven.
"But blessed are your eyes, because they see; and your ears, because they hear. For truly I say to you that many prophets and righteous men desired to see what you see, and did not see it, and to hear what you hear, and did not hear it." (Matt. 13:16-17)
Thank you, Jesus for coming into the world. And Merry Christmas to everyone!