Mezuzah: Protective Amulet or Religious Symbol?” is conveniently available on Rabbi Slifkin’s Rationalistjudaism.com website. The article is a must-read for any rationalist Jew. Gordon argues that the rationalist understanding of mezuzah, that mezuzah is a mitzvah which regularly reminds one of one’s obligations to God rather than being a source of mystical protection, was prevalent amongst Chazal.
I add here three points not made in Gordon’s paper:
1) The Gemara (Menochos 31b) states that when writing a mezuzah, the scribe may not shape the text in the overall appearance of “a teepee or a tail”. However, if the start and end of each line are merely not aligned it is okay. What can be the reason for these laws? The Gemara and rishonim do not explain. It appears though that the sages were discouraging the notion that a mezuzah is a protective amulet. The Gnostics and Essenes, who strongly believed in the cosmological value of letters and magical powers of amulets, would write the “holy” names of angels or demons in their amulets in the overall form of a teepee or tail to augment or diminish the alleged powers of these supernatural forces . Chazal did not want the ideas of these mystical groups to infiltrate mainstream Jewish thought, so they said a mezuzah written in such a way is invalid .
2) The addition of God’s name ‘Shaddai’ on the mezuzah’s exterior is not mentioned in the Gemara - the practice only appeared in the early Middle Ages. Rambam writes in Mishneh Torah that it is the “universal custom to write ‘Shaddai’ on the back of the mezuzah”- he makes no objection. However, Rambam strongly believed that mitzvas mezuzah does not supply any supernatural protection; it is mitzvah like any other. Rambam says that those who treat mezuzah as a protective amulet have no share in the world to come (Mishneh Torah, Hilchos Mezuza 5:4) The inclusion of ‘Shaddai’ in a mezuzah subscribes to the thinking that a mezuzah is a form of protective amulet . If Rambam, the rationalist, so strongly believed that mezuzah does not supply a supernatural protection, why does he record this custom with no protest?
It seems that Rambam did not record this custom in order to perpetuate it; rather, in midst of his diatribe against the practice of including angel’s names inside the mezuzah he had to say that the ‘Shaddai’ on the back is not as severe - it will not make the mezuzah possul.
That Rambam mentions a common minhag in his Yad HaChazaka does not necessarily mean he believes the minhag is correct. The following proves this point: Rambam in his Mishna Commentary (Gittin 5:8) launches a lengthy polemic against the widespread practice of calling a kohen am ha’aretz to read from the Torah before a yisroel talmid chochom. He expresses his displeasure with this custom in no uncertain terms. However, in Yad HaChazaka (Hilchos Tefillah 12:18) Rambam simply says “the common custom today is that even a kohen-am ha’aretz is called to the Torah before a yisroel-talmid chochom.” He doesn’t add any comment regarding his true feeling toward this custom. This demonstrates that Rambam may cite customs that he does not approve of, which appears to be the case for the custom of writing ‘Shaddai’ as well.
3) Rambam doesn’t mention the custom of writing ‘kuzu bemuchsuz kuzu’ on back of the mezuzah, only ‘Shaddai’. The Tur (Y.D. 288) describes this custom as minhag of the Jews of Germany and France. The kuzu’s significance is rooted in the belief that the written names of God and specific letter combinations have deep mystical and cosmological value. These mystical letters augment the mezuzah’s protective powers . These beliefs were the teachings of the school of the Chasidei Ashkenaz . Rambam outright rejects these notions in Moreh Nevuchim (1:61-62), describing their adherents as “fools who believe anything.”
An exception amongst the European rishionim was Rabbainu Avigdor Katz of Vienna (c. 1250) who directed all of Austrian Jewry to refrain from adding ‘kuzu bemuchsuz kuzu’ or Shaddai to the back of their mezuzos . R. Yosef Caro writes “in our time we do not have this custom” of writing kuzu . It can be assumed he is speaking (at least) for the Jews of Spain, Portugal, Greece, Bulgaria, Egypt, and Eretz Yisroel, the countries he had lived in. As late as 1777, R. Refael Elazar Nahmiaś, a leading rabbi of Slonika, testifies that the minhag of the Sefardim is not to write kuzu on the back of their mezuzohs. He goes as far as to pasken that a mezuzah with extra writing on its back should be placed in geniza and not used for mitzvas mezuzah, based on the words of Rambam ! The historic customs which exclude the kuzu bemuchsuz kuzu inscription may hint at an underlying rationalistic approach to the mitzvah of mezuzah.
Do you have a rationalist mezuzah on your doorway? Most probably not. Nowadays all mezuzos are written with ‘Shaddai’ and ‘kuzu bemuchsuz kuzu’ on their backs. However, if you wish, you can contract a sofer to write a mezuzah without these mystical additions. Note though that you must make sure that the sofer does not use the mikvah before writing the sheimos inside the mezuzah. The Rambam considers such a person a fool - a disqualification for writing tefilin and mezuzos:
You must beware of sharing the error of those who write amulets (kameot). Whatever you hear from them, or read in their works, especially in reference to the names which they form by combination, is utterly senseless; they call these combinations shemot (names) and believe that their pronunciation demands sanctification and purification, and that by using them they are enabled to work miracles. Rational persons ought not to listen to such men, nor in any way believe their assertions. (Rambam, Moreh Nevuchim 1:61- Friedlander translation)NOTES
 See Julius Eisenstein’s entry in his Otzar Yisroel Vol I pg.103 s.v. “abracadabra”. http://hebrewbooks.org/pdfpager.aspx?req=2589&st=&pgnum=119&hilite=
 The Talmud records a magical utterance “shabriri, briri, riri, iri, ri…” which rids one of demons and evil spirits. Rashi explains that shavriri is the name of a demon. By saying his name repeatedly, each time removing one letter of his name, the demon is scared away. R. Hai Gaon (Otzor HaGaonim Peshachim 115b) says he does not know the origin of the lachashin mentioned in the Talmud. They seem to come from the Gnostics and like-minded groups.
 See Zohar Parshas Va’eschanan and Maharsha to Brochos 15b.
 Beis Yosef Y.D. 288:15 citing Re’em
 See Tur O.C. 113 and Siddur Chasidei Ashkenaz pg .221.
 Ikkrei Dinnim Y.D. Hilchos Mezuza 14. A streak of rationalism can be seen in the halachic rulings of R. Avigdor Katz of Vienna (teacher of Shibbolei HaLeket). He maintains that the minhag to pray and donate charity to elevate the souls of the deceased is futile (Beis Yosef O.C. 284:7). See Rabbi Slifkin’s article here.
 Beis Yosef Y.D. 288:15
 See his sefer Hon Rav- http://hebrewbooks.org/pdfpager.aspx?req=200&st=&pgnum=22&hilite=. The Sephardim have more recently started to add kuzu bemuchsuz kuzu probably due to the influence of Ashkenazic custom or kabbala.