The other day I came across a statement, seemingly trivial, that to me unlocked one of the mysteries of Western civilisation. Here it is. Alphabets with vowels tend to be written from left to right. Those, like biblical Hebrew, that contain only consonants but not vowels, tend to be written from right to left.

Why did I find this so interesting? The brain, as we know, has two hemispheres which specialise in different functions. The left brain is analytical, detached, linear and logical. It splits things into their components. The right brain is holistic, integrative, even intuitive. It is good at recognising patterns and handling personal relationships, including nonverbal expressions. It plays a big part in emotional intelligence. The neuroscientist Robert Ornstein calls it the seat of creativity and the soul.

The left hemisphere controls the right side of the body, and vice versa. When we move our head to the right, we are using the left hemisphere. When we move it to the left, we are bringing the right hemisphere into play.

When we read something written in an alphabet, like English, that contains vowels, each word is more or less intelligible on its own. So we can use the linear, sequential left brain, which controls rightward movement, which is why English is written from left to right.

Not so when we read a text written in an alphabet without vowels. Imagine English without vowels. The letters ht, for example, might mean any of hot, hat, hit, hut, heat or hate. How do you tell which? Only by understanding the context, and perhaps even how the sentence ends. For that you need to use the integrative and holistic right brain, which controls leftward motion. That is why vowel-less alphabets tend to be written from right to left.

So what, you might say. But now throw two other facts into the mixture. The world’s first alphabet was the proto-Sinaitic script, dating back to around 1,900BCE (Before Common Era). It was the precursor of biblical Hebrew, which went through a variety of letter forms but which remains an alphabet of consonants without vowels (though these are sometimes indicated by non-alphabetical markings).

The world’s first full alphabet with vowels was Ancient Greek, in the early 8th century BCE. Originally Greek, like Hebrew, was written right to left, then snake-wise (called boustrophedon), changing direction at the end of each line. But by the 5th century BCE it had stabilised as left to right, setting the pattern for virtually all other alphabets with vowels.

Putting this together with what we know of the different functions of the brain hemispheres, we begin to understand why Ancient Greece gave the world its first science and philosophy, two supremely left-brain activities. Equally, we can see why the thought-world of Ancient Israel, with its integrative vision of monotheism, was so different. The Hebrew Bible, with its emphasis on personal relationships — the love of God, neighbour and stranger — is a right-brain work.

We can go farther still and speculate how Christianity became a synthesis of the two. Its founder was Jewish and steeped in the religious values of Judaism. But the first Christian texts were written and read in Greek. The result was a set of right-brain ideas transcribed into a left-brain alphabet and culture. Out of that creative tension, Western civilisation was born.

The corollary is equally important. The human mind is the product of both hemispheres. If the connections between them are broken, the result is dysfunction of the personality. We need both: the analytical left brain that allows us to take things apart to see how they work, and the integrative right brain that puts things together to see what they mean.

Religion needs science; science needs religion. They go together like the twin hemispheres of the brain.

Sir Jonathan Sacks is Chief Rabbi of the United Hebrew Congregations of the Commonwealth