What Torah Sources Tell Us to Use Seichel (Common Sense)?

Dear JITC-

I was told by my rabbi that the fifth book of the Shulchan Aruch is seichel, but what sources tell us that we should use seichel (our common sense)?


Dear Malky-

If you want to see a source that we should use common sense, look no farther than the Torah itself. If you read all of the prohibited sexual relations, you’ll notice that father-and-daughter isn’t listed. However, grandfather-and-granddaughter is listed as such a prohibition. Common sense tells us that if grandfather-and-granddaughter is forbidden, then father-and-daughter is certainly prohibited. Accordingly, this is counted as a Biblical (not rabbinic) prohibition, one of the 613 mitzvos and a capital offense – all based on common sense!

The Talmud is replete with arguments based on the 13 hermeneutical rules. The most basic of these is the kal v’chomer, i.e., the argument a fortiori. (Basically, “Superman is stronger than Batman. If Batman can lift 200 lbs., then certainly Superman can, too.” That’s just common sense.) While some hermeneutical rules require a received tradition to apply, any of the Sages could propose a kal v’chomer. They’re all over the Talmud and much of our law is based on them.

The origins of the idea that common sense is the fifth cheilek (volume) of Shulchan Aruch (the code of Jewish law) are nebulous. Jewish historian Joseph Telushkin attributes the phrase to Rav Chaim Soloveitchik (1853–1918). According to Telushkin, a student approached Rav Chaim and asked to be ordained. The rabbi started the exam by asking the student to name the five volumes of Shulchan Aruch.

“But Rebbe,” the student objected, ostensibly correctly, “there are only four volumes in the Shulchan Aruch!”

“There is a fifth,” Rabbi Soloveitchik corrected him. “It’s common sense and it’s necessary to be able to apply the other four.”

In a note, Telushkin acknowledges that the story – or variations of it – have been attributed to other authorities. I have seen it attributed to the Chazon Ish (Rav Avraham Yeshaya Karelitz – d. 1953) and the Kotzker Rebbe (Rav Menachem Mendel Morgensztern of Kotzk – d. 1859 – though he seems too early an authority to have been the source of the idea). Apocryphal though the source may be, the sentiment has been accepted as valid and the concept has been addressed by many contemporary authorities.

I’ll share a story about common sense involving Rav Moshe Feinstein (d. 1986), widely considered the preeminent authority of his generation. Rav Moshe received a call from a young man who had lost his father the week before he was to be married, with the result that his aufruf (the Shabbos before the wedding) was to fall during the week of shiva. Rav Moshe addressed the halacha as it should be observed in these complicated circumstances. A few minutes after the phone call ended, Rav Moshe called the groom back. He realized that the Shabbos of shiva was not only the groom’s aufruf, it was also the bride’s “Shabbos kallah.” He said that if the bride did not receive flowers from him, she would be embarrassed in front of her friends. Despite being in shiva, he said, the groom should therefore be sure to send his bride flowers.

You can scan Shulchan Aruch all you like but I’m pretty sure you won’t find “send your bride flowers for her Shabbos kallah even if you’re sitting shiva” written anywhere. That’s in that fifth, unwritten volume: common sense.

Common sense is necessary to know when to apply the laws in the written volumes of Shulchan Aruch. Are you so sick that you should eat on a fast? Is it too cold to eat in a succah? Should you play music during the Three Weeks in order to keep yourself awake on a long night drive? It’s one thing to know the laws, it’s quite another to know when to apply them. For that we need to exercise good judgment, which requires having common sense.

What’s important to remember is that common sense is used to properly apply the laws in Shulchan Aruch; its purpose is not to supplant those laws. That’s what Korach sought to do in his rebellion against Moshe, as elaborated by Rav Joseph B. Soloveitchik (“the Rav,” a grandson of the aforementioned Rav Chaim Soloveitchik) in his article “The ‘Common-Sense’ Rebellion Against Torah Authority.” If one blue thread in a garment fulfills the mitzvah of techeiles, Korach posited, then surely a garment made wholly of blue wool must suffice. Korach’s goal was to toss out the first four volumes of Shulchan Aruch and to rely on common sense alone. That doesn’t work. The Rav writes:

“The halakhic legal system…has its own methodology, mode of analysis, conceptualized rationale, even as do mathematics and physics… Just as mathematics is more than a group of equations, and physics is more than a collection of natural laws, so, too, the Halakhah is more than a compilation of religious laws. It has its own logos and method of thinking and is an autonomous self-integrated system. The Halakhah need not make common sense any more than mathematics and scientific conceptualized systems need to accommodate themselves to common sense.”

If you were to drop a tennis ball and a bowling ball from the top of a tower, common sense would tell you that the bowling ball would hit the ground first. Common sense says that light must be either a particle or a wave. Common sense declares it obvious that 0.999… is smaller than 1.0. All of these assumptions are wrong because, as the Rav states, math and science have rules that defy our common sense. If we relied on common sense alone, we’d probably all be geocentric flat-earthers.

Like math and science, the Torah has some counterintuitive rules, and this isn’t limited to the para adumah (the red heifer, which famously cleanses impure people but simultaneously renders unclean the pure people who prepare it). Common sense has to operate within the Torah’s parameters, not to the exclusion of them.

Just like a person without a scientific background can’t intuit what a chemical reaction will be, a person with no Torah knowledge can’t discern a proper halachic course of action based on common sense alone. Those who attempt to do so, however sincerely, are following – perhaps inadvertently – in Korach’s rebellious footsteps. Conversely, halacha doesn’t exist in solely on the printed page; it exists in the real world, which has a lot of moving parts. “Seichel” is what one who is proficient in the laws must use when determining when to apply those laws. This occurs within the Torah’s system, which includes chukim (counterintuitive laws). We therefore need both pieces – the Shulchan Aruch plus that elusive fifth volume – in order to reach appropriate outcomes.

Rabbi Jack Abramowitz
Educational Correspondent
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