You probably mean writing or writing system (not calligraphy, which is a sort of DECORATIVE use of writing).

Anyhow, I do not think there is a direct connection between the two. But indirectly – yes. Both Pahlavi and Arabic writing systems come from Aramaic and therefore there may be some sort of similarity between some of the letters.

But being not a specialist in the area I cannot be more specific.

I have no expertise about this, but I asked for information.

"The Pahlavi language is a Indoeuropean language but the script is Semitic. So the writing from right to left and connected letters and multiple morphology of the script resembles Arabic calligraphy. It needs to be mentioned that by the Pahlavi stone inscriptions the letters are written separated and it is different from Pahlavi scripts in books". Thanks to Dr. Shahrokh Raei (Freiburg) (from an Iranian friend of mine).

Hi,

First of all, I´m not fully qualified to answer this question. Mainly because I'm just a student starting a long path to understand a little more about how we got here!

Secondly, some clarifications are needed in order to be more assertive. Starting with "Calligraphy"; it could have multiple meanings, in an informal environment is just synonym for "handwriting", in a more academical sense it is a form of art. The word itself came from classical Greek καλλιγραφία, compose by κάλλος kalli "beauty/beautiful" and γραφή graphẽ "graphics/writing", so it is the art of making visually appealing expressive and meaningful signs.

On the other hand "Epigraphy" (also from Old Greek: ἐπιγραφή, epigrafí "inscribed on/inscription") is a science that studies those same inscriptions, also knowen as epigraphs, as a writing mean of transmitting information.

Your question is, I believe, why Pahlavi script is similar to Arabic script?

They are not! But we will get there shortly!

Languages can be written in a multitude of scripts.

Turkey national language, quite originally known as "Turkish", was traditionally written, for centuries, with Arabic script until President (and Nation Father) Atatürk introduce the variation of the Latin alphabet in 1928 (oddly enough the individual sounds of letters are very similar to the Portuguese alphabet, with the exceptions of the letters "c", "I", "ğ", "ş" and "ç").

Serbo-Croatian is a Slavic language (Southern branch) and the main language of Serbia, Croatia, Bosnia-Herzegovina, and Montenegro (so it should be called Serbian-Croatian-Bosnian-Herzegovinian-Montenegrin). It is a pluricentric language with many local variations but mutually, and totally, intelligible. Throughout history, this language has been written in many different scripts; Glagolitic, Cyrillic, Arabic, Greek, Latin (and its variations like Gaj's Latin).

The same could be applied to any language; Sumerian cuneiform scripts were adopted by the Akkadians; even if the latter spoken a Semitic language that makes the use of a syllabary a poor choice for a script (harder to learn).

But, just to make things more interesting, the Pahlavi script had several forms, the two most recognized are "Inscriptional Pahlavi" and "Book Pahlavi". Both were used mainly (but not only) to write "Middle Persian" (a much better description of the language than usual "Pahlavi language" expression!). It is quite interesting this historical first example of scripts for different uses; one for documents and one for stone inscriptions. The latter is indeed closer to the angular writing of the Arabic Naskhī script, although the Pahlavi form predates it by some centuries.

In modern-day we also use slightly different scripts for different uses in an ordinary way. My handwriting is rather different from this computer-generated text.

Since the very beginning of Islam, also two kinds of scripts existed, one was used for everyday needs and the other was used mainly for copying the Quran. The first is that Naskhī script. It was developed about 1000 A.D. (or the 4th century of the Islamic era, as you wish). It is a cursive, highly legible with particular care on horizontal alignment and letters proportionality style of Script (as the Pahlavi).

Both (Naskhī and Pahlavi) are originated from the same source; the Aramaic Script and from the same context and needs. Is this relevant?

No.

Also, the Hebrew, the Nabataean, the Palmyrenian, the Syriac, as well as literally hundreds of other writing systems (some still used) descend from the Aramaic alphabet...and they are not similar right?!

In conclusion; they are related...vaguely. But is highly doubtful that any direct influence exists able to explains the superficial (and subjective) "similar appearance" between those two scripts.

P.S.- For instance "hrōmayiig ii mu-zrayiig-manišn abar awurd ud be sōxt" is Middle Persian written in an (almost) English/Latin script.