The Eternal Halachah…

[From "Be-Ahavah U-Be-Emunah" – translated by R. Blumberg]

Question: It seems like there are Rabbinic decrees that are no longer relevant, and their rationale has already ceased to hold true. For example, “Mayim Acharonim - washing one’s hands at the end of the meal" was enacted due to the prevalence of salt from Sedom, which could cause blindness, but now that salt is no longer prevalent. So why continue washing “Mayim Acharonim”?
Answer: Indeed, sometimes there is a Rabbinic decree whose status as binding depends on its rationale continuing to hold true. Regarding "Mayim Acharonim," Tosafot (Berachot 52) wrote, “We, however, amongst whom Sodom salt is uncommon, are unaccustomed to washing after the meal,” and the Shulchan Aruch wrote the same thing (Orach Chaim 181:10). We have a rule that if our Sages enacted a decree based on a vote in which the majority quorum prevailed, then even if the rationale behind it has ceased to apply, it still requires a majority quorum of Sages to nullify it, and it does not become null by itself (Beitzah 5a). Yet if, a priori, the decree was only enacted in specific locales where the reason for the decree is relevant, then even in a place where that decree was enacted, if the rationale disappears, the decree becomes null by itself. Pri Chadash therefore wrote that we are unaccustomed to washing "Mayim Acharonim" after the meal, for salt from Sedom is not common among us. Even though it was originally enacted by a majority quorum, another majority quorum is not required to nullify it, because salt from Sedom is not common everywhere, and the original decree was only meant to apply in a place where the danger was present (Yoreh Deah 116:1).
All the same, many of the Acharonim (later authorities) hold that even in our own times we should wash "Mayim Acharonim" because another reason applies, that “dirty hands disqualify one from reciting a blessing… ‘Be holy’ (Vayikra 19:2) – this teaches us about 'Mayim Acharonim' (Berachot 53a). This law applies, obviously, not just regarding the blessing after meals, but regarding someone who eats a piece of fruit at the end of the meal and recites a blessing before it, and his hands are not clean (Orach Chaim 181, Mishnah Berurah #23). Yet there are people who eat with a fork and knife and do not touch their food. According to what precedes, they should not have to wash "Mayim Acharonim" (Responsa Mor U’Ktzia). Yet the Acharonim still reinforced this ordinance, mentioning that there is also a rationale based on the mystical tradition mentioned in the Zohar (quoted in Orach Chaim 181, Mishnah Berurah #22, in the name of many authorities). In other words, when our Sages enact an ordinance or a decree, they do not always reveal all their reasons. Yet if someone refuses to conduct himself according to the mystical tradition, arguing that laws based on the secrets of the Torah do not bind him, we can argue against him by saying “Lo Pelug” – we do not distinguish between different types of rationales. Or, in modern terms, we “generalize.” When our Sages enacted a decree, they did not wish to go into infinite detail about when it is binding and when not. Rather, they fixed simple rules in order not to confuse people with complex deliberations about every case. It is true that according to this, an enactment will probably apply even in cases where it is irrelevant, yet that is a negligible burden compared to the need to judge each instance per se. We should not have to make certain in each instance whether or not the ingredients of the salt have changed, or especially, to examine to see if our hands are clean or not, including the question of just how clean our hands have to be. This way, we do not have to sit at the end of every meal pondering our fingers. Moreover, Rambam explains that the same rule applies regarding Torah law as well. The Torah itself has a general situation in mind, and not exceptions, and we cannot make the Torah fit every individual in accordance with the data applying to him. Otherwise, “the Torah would be given over to measurements” (Shabbat 35b), it would be only relatively and not absolutely binding. We cannot make mitzvot suit the changes undergone by individuals and the times the way medicine does. Rather, the Torah’s laws must be absolute and far-reaching. As it says, “There shall be one law for the entire congregation” (Bemidbar 15:15; Guide to the Perplexed 3:34). Rabbi Shem Tov ben Shem Tov in his commentary there states that the same applies regarding the laws of nature. For example, Rain represents an enormous kindness for the human race, but sometimes too much rain can cause damage. G-d’s calculation relates to people in the aggregate and not to the individual, and out of this calculation the individual benefits as well – even if sometimes it hurts him.