Dressing Up on Purim
Please note that in past years, Rabbi Meir's pre-Purim column consisted of "Purim Torah", light-hearted spoof in the Purim spirit. The following column, although on a Purim topic, is totally serious.
One of the most prominent customs practiced today on Purim is to dress up in costumes, and this custom is mentioned already in the Rishonim. The Rema mentions that it is acceptable even for men to dress up as women (although there are dissenting opinions), even though this seemingly violates the prohibition of "A man's clothes shall not be on a woman, and a man shall not wear women's clothes" (D'varim 22:8). Others mention that is customary to dress up as non-Jews, although this seemingly violates the prohibition "don't go in their ways" (Vayikra 18:3).
Here is one explanation of this custom.
The prohibition to be likened to non- Jews exists at several levels. In general, this prohibition, like other Torah prohibitions, should not stand in the way of danger, and indeed the Shulchan Arukh writes that a person may dress up like a non-Jew to avoid being identified as a Jew if Jews are being attacked (YD 157:2). However, if there is a decree for Jews to dress like non-Jews in order to make us lose our distinctiveness, then we are forbidden to change our dress even in the face of danger (YD 157:1).
Likewise, entering a place of idolatrous worship is normally forbidden; however, it is permissible in order to escape danger, but forbidden if the danger arises from a decree against Jewish worship.
In other words, the degree of prohibition depends on the motivation of hostile non-Jews. If their objective is to make us give up our traditions, then we must resist at all costs. But if their enmity is irrespective of our customs, then we can be more lenient. I heard from a prominent Rav that in the time of the Holocaust the rabbis were particularly lenient, because the object of the Nazis was not at all to make us give up our customs; on the contrary, they explicitly included in their mass killings people of Jewish background who did not even identify themselves as Jews.
At the time of Purim, the decree of Haman was directed against all Jews. It is true that the stated reason behind the decree was Haman's claim that we were a people who didn't keep the king's laws (Esther 3:8), but this was not Haman's true motivation, and in any case the decree applied to all Jews.
In this case, dressing up as a non-Jew would have been permissible. So the custom to dress up as non-Jews reminds us that this practice would have been permissible at the time of the original miracle, due to the unique nature of Haman's decree.
Another possible explanation is that the non-Jews at that time likened them- selves to Jews, as the Megila states 'And many of the common people Judaized themselves" (Esther 8:17). We commemorate and mock this insincere, purely external adherence to Judaism by adopting a purely external likeness to non-Jews while internally remaining fully devoted to our faith.