I believe in one God is the English translation of these words in Greek Πιστεύομεν εἰς ἕνα Θεὸν and in the liturgy it is Πιστεύω εἰς ἕνα Θεόν and the Latin equivalent is Credo in unum Deum when it is said in the liturgy. It seems almost too ordinary to be worth comment yet when it was formulated it was a beacon of light shining in a polytheistic empire where the followers of paganism vastly outnumbered Christians. It was also a controversial proclamation because it implied that not only were the pagan gods not believed in by Christians but also that the emperor was not a god in whom Christians placed any faith. And when it is noted that the first Nicene council was summoned by a Roman emperor who was (until recently) regarded as a divinity it becomes obvious how subversive of the order of things that then existed the opening words of the creed really were.
I believe, it says, rather than stating "God is one" it starts by affirming my belief in the oneness of God. My belief as a follower of Jesus Christ. My belief as one who hopes in one God and is willing to give up the gods and the values of a culture that conquered the known world. A culture that was vigorous and powerful and thoroughly polytheistic.
Today believing in one God in an English speaking nation is commonplace, almost the norm, or so it seems. Yet the words of the creed still have power to shock; try saying "I believe in one God" to your work mates, your sporting friends, your family and perhaps you'll see how controversial the words still can be.
"I believe in one God" shakes the foundations of every kind of self-sufficiency because the one God in which I believe is not me.