Megillah 18 - How to write a Megillah?

To write a new Megillah, one must copy it, word for word, from an existing scroll. In general, this is true for all scriptures. Incidentally, if one were to write a new Megillah on Purim, copying it out of the existing scroll and pronouncing every word, he has fulfilled his obligation of listening to the Megillah reading on Purim.

But, what about the following story: Rabbi Meir went for an urgent matter, to intercalate the year, to Assya. There was no Megillah there, so he wrote it from memory and read it. Rabbi Meir was a different kind of human being. The complete Torah was always in front of his inner eye, so it is as if he wrote it by copying from a scroll. And yet, the Sages forbade writing from memory!? - in case of pressing need, it is allowed.

But what about tefillin and mezuzah that can be written from memory? This seems to contradict the rule? - Tefillin and mezuzah are known by heart by many. The scribe can write them, provided that he is certain.

Art: Jewish scribe. Jozef Israëls