Ἐν ἀρχῇ ἦν ὁ λόγος, καὶ ὁ λόγος ἦν πρὸς τὸν θεόν, καὶ θεός ἦν ὁ λόγος (John 1:1)
The standard translation of the incipit of St. John Evangelion is: “In the beginning was the Word, and the Word was with God, and the Word was God”. A better translation of the Greek word ὁ λόγος would be the Latin “ratio”. In English the best bet is probably to keep the word “Logos”.
If as Bertand Russell says in “History of Western Philosophy” (HWP, pg. 56) Pythagorism is behind Plato’s philosophy (“Let no one untrained in geometry enter”) and much of Western “intellectualized theology” and if, as Nietzsche said, Christianity is “Platonism for the masses”, then the Evangelical phrase has a different interpretation, the following.
In methaphoric parlance, the mathematical structure of the universe (the “Logos”) was there at the beginning, in some Platonic realm. But this mathematical structure of the universe (think to Spinoza’s “deus sive natura“) had to descend upon our species of primates in order for us to make sense of the world. In a more precise sense, in the words of cosmologist John Barrow (Pi in the Ski, p. 295) “the utility of mathematics for our understanding of the world is a reflection of the ubiquity of computable mathematical functions”. Evolution did the rest, attuning our minds to this inner structure.
“Καὶ ὁ λόγος σὰρξ ἐγένετο” (John 1:14: “and the Word became flesh”) which translates in this interpretation into “the mathematical structure of the universe became embedded in our mind”.
The unreasonable effectiveness of mathematics is not that unreasonable, if contemplated from such a vantage point. The whole structure of Western science rests on this unstated assumption, that our finitude is capable of touching upon the infinite in its very essence of what is beyond time and space (the mathematical structure of the universe). This was Pythagoras then Plato, S. Thomas, Descartes, Spinoza, Leibniz, Kant. See again Russell, History of Western Philosophy.
Others gave a simpler interpretation, more palatable to the (average) cultural level of the first century A.D. But the meaning does not change.