'In the beginning was the Word, and the Word was with God, and the Word was God.' These are among the most famous lines in the New Testament: they begin the Gospel of St. John. But what does 'In the beginning was the Word' mean? Let's take a closer look at the meaning of this famous opening sentence.

It's perhaps helpful to begin by setting out the difference between the Gospel of John and the three other gospels: Matthew, Mark, and Luke. The Gospel of Mark is thought to have been composed the earliest of the four gospels, with Matthew and Luke basing their own accounts on it. The gospel of John was written later still, and of the four, has the strongest claim to actually having been written by one of Jesus' apostles. (It's been speculated, though we cannot know for sure, that John may have written his account in the late first century AD, when he was an old man of nearly 90.)

Matthew, Mark, and Luke are grouped together as the 'Synoptic' gospels, from a word meaning 'seeing together'. These three accounts all reflect each other to varying degrees. But the Gospel of John is quite different. Right from those opening words, 'In the beginning was the Word, and the Word was with God, and the Word was God', John is signalling that his account of Jesus' life will be treating Jesus as much more than a human being. This is not to say that the other gospel writers don't also acknowledge that Jesus is the Messiah (as well as a human being), but that John's Jesus is supernatural and ethereal – otherworldly, almost – right from the beginning.

'In the beginning was the Word.' But what does John mean by 'the Word'? The original Greek text has Logos, for which 'the Word' is our English translation. But Logos is a word that comes with a lot of meanings packed into it, and 'the Word' is only a partial reflection of this densely significant word. This term, 'the Word', is not found in the Old Testament, and its use in the New Testament is down entirely to John.

In his endlessly informative Asimov's Guide to the Bible: The New Testament: 002, the author and all-round polymath Isaac Asimov links John's 'In the beginning was the Word' to the Greek philosophy of Thales of Miletus, who lived in the seventh century BC. Thales argued that, contrary to the idea that the world was largely erratic and unpredictable in its operations, it was actually subject to rigid laws of nature, and that these laws could be discovered using reason and observation. This is the beginnings of both rationalism and empiricism, if you will.

This meant that God – or, depending on which belief system you subscribed to, a whole pantheon of gods – created the world upon some clear and knowable principle, and that this principle is constant rather than changeable and arbitrary. One of Thales' followers, Heraclitus, used the term 'Logos' to refer to this rational principle. 'Logos' means 'word' but it also denotes the entire rational structure of knowledge as Thales and Heraclitus had theorised it.

And as the term 'Logos' was taken up by more and more philosophers, it came to refer not to some abstract entity but to a thing, even a person: the person who had created this orderly system of knowledge and principle in the world. Logos, if you will, became personified. This tradition spread beyond the Greek world, and was taken up by the Jewish followers of Yahweh, or the Old Testament God. In Jesus' time, a man named Philo the Jew popularised the term Logos as a reference to the rational aspect of Yahweh.

So when John begins his gospel by taking us back to the very beginning – of time and of the world and the universe – he is using the term Logos in light of this thinking. So 'In the beginning was the Word' means 'In the beginning was Logos' which means 'at the beginning of everything, there was the entity we know as God, who embodied, and created, the rational principle on which everything is founded'.

So much for 'In the beginning was the Word'; but what about the next part of John's sentence? How was 'the Word' with God as well as being God?

Well, as Asimov explains, at the time John was writing there were some philosophers who tried to keep God and Logos separate. Logos was not synonymous with God, but merely one power that he possessed, if you will. God, being spiritual, was removed from the rational and scientific processes of the world: he could not be associated with material things, as an elision of 'God' with 'Logos' would imply. These philosophers and mystics were known as 'Gnostics', from the Greek meaning 'to know'.

For these Gnostics, because the world is material, God could not have been directly responsible for creating it. Instead, they believed some sub-divine and more malevolent entity had done that. Because the world is full of evil, the Gnostics reasoned, an evil being must have had a hand in its creation. Plato famously called this being the 'Demiurge'. And for Gnostics, Yahweh – the Old Testament version of God – was really the Demiurge, this inferior being to the true God, and the Demiurge was the one who had brought the (flawed) world into being.

For the Gnostics, Jesus was the true God, as opposed to Yahweh, the creator and Demiurge. And the Gospel of John, and those opening lines, set themselves against such a Gnostic interpretation of God and Creation. God and Jesus, God and Logos, Logos and Jesus: all are one and the same. Or, as John more poetically (but obscurely) puts it: 'In the beginning was the Word, and the Word was with God, and the Word was God.' That is, at the beginning of all things there was Logos, the creator of everything. And Logos was not only with God, but Logos was God. As the succeeding two verses of the Gospel of John make clear, Logos and God are the same being:

1:1 In the beginning was the Word, and the Word was with God, and the Word was God.

1:2 The same [i.e., Logos, the Word] was in the beginning with God.

1:3 All things were made by him; and without him was not any thing made that was made.

That is, Logos was God, and Logos made 'all things'. God made all things, but God was Logos, or the Word.