Why is Arabic Written Right-to-Left?

This is the Qur'an... and this is 1001 Nights.

Notice anything?

These are the front covers, though someone used to writing a European

or Indian language might expect these to be the back covers!

Arabic reads from right to left, while English or Russian or Tamil reads from left to right.

If you look at the arabic script in context, along with the rest

of the Phoenician-derived script systems, it's actually quite rare in this aspect.

Of all these writing systems, it's just Arabic, Hebrew,

and a few smaller writing systems like Syriac and Samaritan that are written this way round.

So why is Arabic written right to left?

Let's take a look at this map of the Phoenician-derived scripts. Phoenician,

the common ancestor of these scripts, descends from Proto-Sinaitic,

the first traces of alphabetic writing that we have at all.

And those are thought to come from Egyptian hieroglyphs.

The Sinaitic family is the largest family of scripts in the world, and it includes the Latin,

Greek and Cyrillic alphabets, the Indic abugidas, the Arabic alphabet, and well...

Scripts like Arabic and Hebrew are more precisely described as "abjads",

because rather than representing all sounds as independent letters like Latin does,

they only represent consonant sounds, with vowels being left up to context, or to

diacritic markings in vocalised scripture, like here, with each of these little accents

telling the reader what vowel comes after the consonant letter it's modifying.

Now back to Proto-Sinaitic, which is also technically an abjad.

Just like the Egyptian hieroglyphs it comes from, this script was probably written in either

direction, with the way the symbols were facing determining which direction to read them in.

The main two descendants of Sinaitic were Phoenician and the South Semitic family.

Almost all of this branch has now completely died out, with the exception being Ge'ez,

the abugida script of Ethiopia, which, surprise surprise, also reads left to right.

Phoenician, meanwhile, was an abjad,

which could, like its ancestors, be written in either direction...

but as it became standardised, it began to have a consistent right to left direction.

Now, its descendants were...

Wait, right to left?

Left to right, no?

No. Right to left. the same direction as Arabic.

Actually both phoenician and the ancestors of the Ge'ez script were written right to left,

suggesting that this was the preferred direction of the late era Sinaitic script altogether.

So the question isn't really why are Hebrew, Syriac,

Samaritan and Arabic written right to left?

The question should be why aren't... Ge'ez, Latin, Cyrillic, Greek,