There’s been a lot of talk floating around the internet in the last week regarding Schlissel Challah, the custom of baking challah either in the shape of keys or with an actual key pressed into the bottom on the shabbat after Pesach. While slim to none of the participants have been in support of the custom, opinions have ranged from thinking of Schlissel Challah as a pointless but tolerable practice to thinking of it as actual Avodah Zarah. Many have used the minhag as a jumping off point for larger discussions about Judaism, such as open-mindedness and hypocrisy, or Hishtadlut (the idea that personal initiative is both necessary and important in everyday life). What these discussions have largely missed is that Schlissel Challah isn’t it’s own phenomenon, rather it is part of a much larger stream of thought in Judaism.
Since its very beginning, Judaism has possessed both Mystical and Rationalist streams of thought. This dichotomy can be found even in the Torah itself, such as in the discussion of the reasons for Korbanot in Vayikra 17:5-7. The presence of this debate in midrashei HaZaL is so prevalent that A.J. Heschel wrote his three-volume magnum opus, Torah Min HaShamayim BeAspeklariah Shel HaDorot, on the topic. This split continued through the generations, with Mysticism peaking with the Arizal and the Kabbalistic Renaissance in Tzefat, and Rationalism probably peaking with Rambam and Ralbag. Schlissel Challah, while it only goes back to the Hasidic Movement, is a manifestation of this much larger debate.
Part of this debate is the question of the greater purpose of mitzvoth. Rationalists tend to view mitzvoth as being for the purpose of Mankind and its improvement, on global, societal, and individual levels. Torah learning enables people to keep halakha and encourages intelligence. Giving tsedakah provides support for the destitute while making the giver more charitable. Mysticism sees mitzvoth as being for the sake of ‘א and the mystical health and sustenance of reality. Learning Torah brings godly sustenance to all levels of reality. The giving of tsedakah is a mystical necessity for the world. While some thinkers, such as Ramchal, created syntheses that utilized aspects of both approaches, most approaches to the purpose of mitzvoth fall squarely into one of these two camps.
One aspect of the debate regarding Schlissel Challah has to do with this idea of spiritual mechanics and the meta-divine. Part of the innovation of Monotheism that Judaism brought to the world was the absence of meta-divine, things that are outside of ‘א. Idolatry is thus based on the idea that there’s something outside of ‘א. This means that any implication of sustenance or help being received via a process, without the direct influence of ‘א, is absolutely forbidden. Thus assuming that putting a key in a piece of bread would cause one to receive more sustenance would be absolutely forbidden. However, that’s not the only way to view segulot such as Schlissel Challah. This negative view assumes that segulot somehow affect a system of reality outside of ‘א, but that’s only one way to conceive of such a system. Such a system of mystical processes could just as easily be a part of ‘א, or a system he set up that is totally within his control. If that were the case then Schlissel Challah would not at all be Avodah Zarah. How you conceive of segulot is just a question of how you conceive of reality, and that is already very subjective.
A perfect example of the way this debate affects mitzvoth is the commandment of Shiluah HaKen, sending away the mother bird before taking its eggs. The rationalist approach to this mitzvah believes that it’s purpose is to make man more merciful. The mitzvah is not an obligation so much as a proper method. It’s not that a person is commanded to take eggs and send away a mother bird, rather if a person is going to take the eggs, then they must send away the mother first, as this is a more merciful method for getting the eggs. The mystical approach is completely different. From the mystical perspective, the command is intended to activate ‘א’s attribute of Mercy to influence the Nation of Israel. Thus the mitzvah of Shiluah HaKen is not simply a method, but a full on obligation. This is more than just a theoretical debate. The first practical difference is whether or not a person should search out eggs to find. From the rationalist approach, this mitzvah is not an obligation. Like the command to give a get, a divorce document, it is simply the proper method to perform a certain task, if and only if a person finds this situation before them. Without the need for the eggs, the mitzvah would decrease a person’s compassion rather than increase it. For a mystic the command is a full-on obligation. The second ramification of the debate isn’t just about whether or not one must perform the mitzvah, but whether one is even allowed to. According to many who say that the mitzvah is a matter of mercy, sending the mother bird away unnecessarily would fall under the biblical prohibition regarding cruelty to animals. Thus a person who did not need the eggs would actually be prohibited from fulfilling the mitzvah. From the mystical perspective this issue does not exist by Shiluah HaKen, and nobody claims that Schlissel Challah is anywhere near that problematic.
The practice of baking Schlissel Challah can be, and has been, challenged on numerous grounds. However, all of these attacks come from a fundamentally different perspective than that of those who actually practice the rite. Challenging Schlissel Challah is itself essentially meaningless, as all a person is really doing is challenging the axioms upon which the practice of Schlissel Challah is based, and thus challenging a very large stream of the modern Orthodox world-view. This isn’t certainly allowed, but a person should be conscious that this is more or less what they are doing when they challenge Schlissel Challah, and it begs the question of if it’s even worth it. As pointed out above, from the Rationalist prospect, Schlissel Challah is hardly as problematic as Shiluah HaKen. The advantage for challenging Schlissel Challah would be its relatively recent development compared to other rituals, but it’s still a matter of differing axioms more than anything else. At that point, one might as well challenge Shiluah HaKen, a rite practiced commonly in the modern era, despite possibly being prohibited on a Biblical level. Cruelty to animals is a big deal, and something that ought to get paid more attention to in modern Judaism. If you’re going to challenge mystical practices, one involving animal cruelty would be a much better place to start. Otherwise, it might be worth getting used to the fact Judaism always has included both Rationalist and Mystical approaches, and it probably always will.
 It’s unclear to what degree practitioners actually believe there is a direct causative relationship between putting the key in the bread and receiving more sustenance. For many, the rite is simply a reminder that ‘א is the source of all sustenance, certainly a Jewish concept.
 It’s worth noting that a person can object to segulot without being a rationalist. HaRav Yaakov Peretz, Shlita, Rosh Yeshiva of the Beit Midrash Sefaradi, is known for saying that he knows of “four segulot better than any others: Torah, Tefillah, Teshuva, and Tsedakah.” While he clearly is not denying the potential validity and power of segulot, he simply believes that they’re not meant to be the focus of a jew’s attention.
 For more information on this topic, see Rav Eliezer Melamed’s Peninei Halakha, a truly excellent resource.
 Ignoring, of course, those who make Schlissel Challah simply as a reminder that all sustenance really comes from ‘א.