# logic behind kol kavua k'mechtza al mechtze

there is a principle in halacha regarding doubts that if something is separated from a kavua (fixed place) it is treated as 50/50% chance even if the permitted is the majority.

but if it is found in the shuk then it goes by the majority.

so for example, if one finds a piece of meat outside and most stores are kosher then the meat is considered kosher.

but if one takes it from a store and it is unknown which store then it is 50/50 doubt even if the majority is kosher.

does anyone know whether there is a rational argument for this or is it just straight halacha without logic?

Rabbi Aqiva Eiger (shu”t #136) says that there are two types of doubt, and each has its own mechanism for birur, for clarification.

The case of qavu’ah is one where the reality was once established. So in principle, there is a specific halakhah assigned already to this case. The doubt is in what that halakhah is. In this situation, we do not invoke rules like rov (majority), and every doubt is treated identically to an equal one.

The case of kol deparish is one where the reality was never established; this item never before stood out from the rest of the set. Therefore, we are assigning a halakhah to a case where the physical reality is in doubt. Here, majority is allowed.

Tosafos (Zivachim 72b, “Ela amar Rava”) write “qavuah only applies to a thing that is known”. Rabbi Aqiva Eiger explains that the piece of meat bought from the known store had an established halakhah. The buyer knew the state of the meat. We therefore call the halakhah “qavu’ah” — established. However, now it got mixed up, and we don’t know what that halakhah is. The doubt is in the halakhah.

However, if the meat is simply found, then the uncertainty begins one step earlier. We don’t know the state of the meat. The doubt is in the reality, what part of the set this item was parish — separated from.

I suggested a theory as to why this was true, based on first principles.

The Chinukh repeatedly explains various mitzvos by explaining “ha’adam nif’al lefi pe’ulaso — a person is affected according to his action.” Contemporary hashkafos differ over what halachic life is supposed to cause, whether the ideal is better described as “wholeness”, perfecting the image of G-d, or “attachment” to G-d…. But notice that both agree in describing the role of halakhah in terms of the change is causes on the self — whether perfecting him in a mussar sense, refining him in a Hirschian sense, bringing him experientially in a relationship with the A-lmighty, as Chassidim do, etc…

One thing this implies is that halakhah need not be concerned with determining an objective reality. Rather, it has to deal with that which has impact on the person — the world as it’s experienced. Perhaps this is why the realia to which we apply halakhah is called metzi’us, literally “what is found”, and substantive elements of the metzi’us are said to have mamashus, they can “be felt”.

Thus, if we do not know the reality, the metzi'us / mamashus is the resulting doubt. And thus, it makes sense that pesaq takes into account likelihood, as that is reflected in my doubt. But if we experienced reality, then halakhah was already established by that reality. And then it's not a matter of doubt, it's a matter of whether we are obligated to "play safe".

(I have what is likely a sefer's worth of material on the interplay of this phenomenology approach to metzi'us and halakhah at http://www.aishdas.org/asp/category/phenomenology . The above was snipped from there.)

• "They" tell that Kavua was one of the 3 Sugyos that R Chaim Brisker never understood. – Double AA Sep 4 '15 at 20:12
• Ah, but I'm a talmid of a talmid (Rav Dovid Lifshitz zt"l) of the author of Shaarei Yosher (HaRav Shimon Yehudah haKohein Shkop)... – Micha Berger Sep 6 '15 at 0:54

Professor Moshe Koppel has written and lectured interestingly on this subject. See http://u.cs.biu.ac.il/~koppel/rov-traditionversion.pdf .

This answer is based on Rishonim in Pesachim 9b. The difference between Kavua and Ruba Deyita Kaman is when the doubt did appeared. Gemara 9b.

תשע ציבורין של מצה ואחד של חמץ, ואתא עכבר ושקל ולא ידעינן אי מצה שקל אי חמץ שקל - היינו תשע חנויות. פירש ואתא עכבר ושקל - היינו סיפא. דתנן: תשע חנויות, כולן מוכרין בשר שחוטה ואחת מוכרת בשר נבלה, ולקח מאחת מהן ואינו יודע מאיזה מהן לקח - ספיקו אסור. ובנמצא הלך אחר הרוב.‏

If there are nine packages of mazzah and one of leaven, and a mouse comes and steals [a package], and we do not know whether it took mazzah or leaven, that is [similar to the case of] nine shops. If [one package] was separated and a mouse came and stole it, that is [similar to] the second clause. For it was taught: If there are nine shops all selling meat of [ritually] slaughtered [animals], and there is one shop selling meat of nebelah, and a man buys [meat] from one of them , but he does not know from which [shop] he bought the [meat in] doubt is prohibited; but in the case of [meat] found, we follow the majority.

The Rashba in Torat Habayit Haaroch Bayt 4, Shaar 1 explains:

ומה שאמרו כל קבוע כמחצה על מחצה דמי הני מילי בשלקח הוא מן הקבוע לפי שהספק נפל לו בקבוע אבל אם לקח אחד מן הקבוע ונפל מידו או שהניחו במקום חוץ ממקום קביעותו ולא נודע אם מן ההיתר המרובה או מן האיסור המועט אין זה קבוע שהרי לא נפל לנו הספק בקבוע אלא בפורש ובכל כי הא אמרינן כל דפריש מרובא פריש והיינו סיפא דתניא ובנמצא הלך אחר הרוב ואעפ"י שדלתות מדינה נעולות ואין בשר נכנס למקום זה אלא מאותן חנויות וכל שבא לכאן מאותן חנויות בא אפילו הכי מותר דהא לא נפל לנו הספק בקבוע אלא בדפריש.

In Shaar 2:

ולפי דברי רבנו יצחק ז"ל אם לקח אדם מן המקולין חתיכה הראויה להתכבד בה בפני האורחין ואחר כך נמצא טרפה במקולין אעפ"י שלא נודע עד שפירשה זו וכשנולד הריעותא במקולין לא היתה זו בקבוע אפילו הכי אסורה גזירה שמא יקח מן הקבוע הואיל ולא נודעו חתיכות הטרפה בין חתיכות ההיתר וכן גם דעת רבנו שמשון ז"ל שכל שנאסרה שעה אחת מחמת קביעותן שוב אינן ניתרין ואפילו פירשו מעצמן

If we seen the mouse that steals something in one of the packages, the doubt is as we need to decipher a photo of the mouse when that take the cookie and the cookie is here. We have no element to help us to decipher the photo.

If the cookie was already out of the packages when we see the mouse, we have not to decipher the same question. The question is from which package comes the cookie. The global existence of the set of package is questioned. The rov can intervene.

But if the mouse leaves the cookie on the street and afterwards another mouse take it and the cookie is here, we have a question about the cookie which is comming with the second mouse from the street.

If when someone take a piece of meat from a store and afterwards only we discovered that one of the stores has a problem of Trevor. There is no problem of kavua meyikar hadin because the halachic question emerged afterwards. (The Raah disagrees and says that retroactively this is a case of kavua)

There is a difference between a question about the reality and a question about Halacha. When we ask an halachic question, we analyze the last step that generates our question. This is not an inquiry because we are not inquiring. So, we see the packages as a set, their are mixed from our point of view. If the cookie came here in one action, we ask about this action. The packages are not mixed. Note that mixture is a view of the spirit. To see pieces as mixed we need a degree of abstraction. To see packages as a whole mixture is an abstraction. This is possible when the senses are not grasping the objects separately.