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Is the principle of Occam's razor (that among competing hypotheses, the one with the fewest assumptions should be selected) discussed or used in any Jewish sources (ideally chazal or rishonim)? Is it given a specific name, or referred to by the name of the Franciscan friar who made it popular?

  • Whoever downvoted and voted to close as off topic, please give an explanation of why. – robev Oct 11 '17 at 18:01
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    Ein davar yotzei miydei peshuto? – rosends Oct 11 '17 at 18:39
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    @rosends I believe the phrase is ein krah yotzei midei peshuto, referring to the verse having a derash that doesn't preclude the peshat. Occam's razor is the simplest explanation is usually the correct one. Ein krah isn't applied when there are competing peshats, and I don't believe the simplest one is usually selected – robev Oct 11 '17 at 18:42
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    How about "Ein Lo la-Dayan Ela Mah she-Einav Ro'ot" (Sanhedrin 6b, Nidah 20b)? – Tamir Evan Oct 15 '17 at 11:22
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    Occam's trimmer> – SAH Oct 19 '17 at 18:51
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Talmud, Chagiga 3b:

ת"ר איזהו שוטה היוצא יחידי בלילה והלן בבית הקברות והמקרע את כסותו איתמר רב הונא אמר עד שיהו כולן בבת אחת ר' יוחנן אמר אפי' באחת מהן היכי דמי אי דעביד להו דרך שטות אפי' בחדא נמי אי דלא עביד להו דרך שטות אפילו כולהו נמי לא לעולם דקא עביד להו דרך שטות והלן בבית הקברות אימור כדי שתשרה עליו רוח טומאה הוא דקא עביד והיוצא יחידי בלילה אימור גנדריפס אחדיה והמקרע את כסותו אימור בעל מחשבות הוא כיון דעבדינהו לכולהו הוה להו דף ד,א גמרא כמי שנגח שור חמור וגמל ונעשה מועד לכל

Our rabbis taught: "Who is regarded as legally insane? One who walks out alone at night, sleeps in a graveyard, and tears his clothing." ... One sleeps in a graveyard at night -- maybe he's doing that in hopes of a spirit visiting him? One who goes out alone at night -- maybe he has a terrible fever! And one who tears his clothes -- maybe he is deep in thought? Once he does all of them, it's a general thing.

As one rabbi commented on that: we would prefer one single explanation (i.e. "the guy is crazy") than three separate explanations.

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  • where do you see the gemarah indicating a preference? Is there any indication that this is a principle vs a disagreement over the definition of insanity? – rikitikitembo Oct 11 '17 at 18:01
  • @rikitikitembo how are you reading it? The gemarra offers three characteristics for a shoteh and the makshan deflects all three since there's an alternative explanation, but once a person does all three, there's no room for deflection, since the simplest explanation is he's a shoteh, thus applying Occam's razor. – robev Oct 11 '17 at 18:29
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    "One rabbi commented"; this is said in the name of R. Chaim of Brisk. – Oliver Nov 23 '17 at 18:40
  • @Oliver Quted in my answer. – Alaychem Remember Monica Jan 13 at 10:25
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From Wikipedia:

כַּאֲשֶׁר תֵּרוּץ אֶחָד מְתָרֵץ שָׁלוֹשׁ קֻשְׁיוֹת, בִּמְקוֹם לְהִזְדַּקֵּק בַּעֲבוּרָן לִשְׁלוֹשָׁה תֵּרוּצִים, הוּא הַתֵּרוּץ הַנָּכוֹן (הרב חיים הלוי סולובייצ'יק)

When a single answer answers three questions, instead of three different answers, it's the right answer. (Rabbi Haim Halevi Solovechik)

הדברים אשר יתבררו מצד הבאת הראיה עליהם ותהיה מציאתם מציאה שאי אפשר לדחותה, אין אנו צריכים להעלות על דעתנו, שהם יותר ממה שהצורך מביא אליו בהשלמת הדבר שהוא לראיה עליהם (רבנו בחיי).

When issues are solved, by a proof that cannot be rejected, we don't need to imagine, that there is more [in those proofs] then what is needed to answer the issue (Rabenu BeHaiei) .

כאשר אנו מעלים במחשבתנו שיעשו שניים נפעל אחד, אם נדמה שהאחד עשה את כולו וגם השני עשה את כולו - יהיה זה הבל, כי אם הראשון עשה את כולו לא נשאר בו לשני מאומה לעשות, ואם נדמה שהאחד עשה את מקצתו והשני עשה מקצתו, הרי כל חלק שייך לעושה אחד ואין לו בו שותף (רבי סעדיה בן יוסף פיומי)

When we imagine that two causes, generate one result, and we think that one of the causes create the entire result, and the other as well, that would be nonsense, because if the first completed the action, the second is needless, and we will imagine that every cause created part of the result, so every part (of the result) belongs to one cause, and the other cause has no partnership in it. (Rabbi Seadya Ben Yossef Pyumi)

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  • If I don't mistake the Rambam cited is in Mishna in Nazir and explains מפני החזקה שרגליים לדבר, it's an other topic – kouty Jan 13 at 10:45
  • Which Wikipedia article – robev Jan 13 at 23:04
  • The Hebrew article about Occam's razor. This article is greatly approximative, particularly the citation from the Rambam. – kouty Jan 14 at 19:42
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I believe the talmudic equivalent would be tafsta meruba lo tafasta loosely translated as 'if you grab too much you grab nothing'. the principle is usually applied to make the smallest inference possible based on the datum. This is not necessarily an exact parallel but in my opinion it is close.

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  • This answer already rejects this. – robev Oct 11 '17 at 17:42
  • @robev true, but the OP's comment on that answer explains why the OP rejects it. – rikitikitembo Oct 11 '17 at 17:58
  • Tafasta merubah means that if I can say that this item is one tefach versus five tefachim we assume it’s one tefach (Sukkah 5a). – DonielF Oct 11 '17 at 18:58
  • @DonielF yes, but why assume that? The linked question is clarifying if it's because of Occam's razor or not. My question is more broad as I'm curious even if tafadta merubeh is unrelated. – robev Oct 11 '17 at 19:24
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    I give +1... It would have been my answer too. – David Kenner Oct 15 '17 at 0:13
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I would reason that the logical method in assessing and assuming the most likely reconciliation for a given contention is a constant in Talmudic analytics. The Talmud is replete (almost expected) in finding the most suitable, simple explanation. It can be argued that this is the underlining rationale in phrases like "במה דברים אמורים" or "הני מילי" when determining a probable and accurate position when confronted with multiple positions.

Among the Rishonim I would assume the principle is parallel (if not close to it) to the common conciliatory phrase "אפושי פלוגתא לא מפשינן" (loosely trans. we don't increase disagreements; a spin on the words in BT Beitzah 7a). The typical application is when confronted with two views and attempt to reconcile them by assuming they disagree as opposed to proposing a fitting solution. It's conventionally assumed that the doctors of the Talmud maintained such line of reasoning. For a single example see Tosafos (Nid. 8b). R. Aaron Maggid did nice research tracing this idea (Bet Aaron vol. 10, 661ff.)

(See also a nice demonstration of this logical principle, how it relates to Talmud study, in Prof. Dov Zlotnick's intro. to Greek in Jewish Palestine.)

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This article compares the PaRDeS method of interpretation to Occam's razor in which the Pshat reading limit to the most modest assumption necessary to resolve exegetical and/or argumentative difficulties.

Curiously, both U. Simon and R. Mordechai Z. Cohen mentions Ibn Ezra approach to pshat as an example of this. U. Simon says (in Four Approaches, p. 180) that this is "the fundamental principle of his method — the aspiration to reduce every daring hypothesis and every marginal method to the absolute minimum". Accordingly, R. Mordechai Z. Cohen (in Three Approaches to Biblical Metaphor, p. 233) name it "exegetical economy".

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It is used in 13 Midot of Rabbi Yishmael in the Kal Vachomer "חדא מתרתי".

I think that we have a good example when the Gemara makes a Kal Vachomer from x1 the mild to y the severe to give it a din A. And the Gemara asks a pircha, x1 has a side n1 that is severe and not attributable to y. Perhaps this side causes the din A. So the Gemara try to learn it in a similar way from x2. But x2 has a side n2. In a next step the Gemara learns A fory from both x1 an x2. And the fact that n1 and n2 are not the same is an argument that they are not the cause of the din A. Here is the Occam's rule. It's not probable that the same din A is in x1 and x2 because of different reasons.

And we make the Kal Vachomer (there is a discussion if it remained Kal Vachomer) from both. The expression is וחזר הדין לא ראי זה כראי זה הצד השווה שבהן וכו'. It's very close to the Occam's razor and is a pure talmudic rule.

See in Sefer Halichot Olam.

פירוש במה מצינו בהצד השוה והיינו לא ראי זה כראי זה ולא ראי זה כראי זה הצד השוה כלומר הואיל ולא ראי זה כראי זה וכו' הילכך יש לך לבקש הצד השוה שבשניהם שגורם אותו הדין ומאותו הצד נלמוד כל הדומה לו, דוגמתו בפרק קמא דקדושין חופה קונה מקל וחומר מה כסף שאינו גומר קונה חופה שגומרת אינו דין שתקנה מה לכסף שכן פודין בו הקדשות ומעשר שני ביאה תוכיח כלומר שאין הדבר תלוי בכך מה לביאה שכן קונה ביבמה כסף יוכיח וחזר הדין לא ראי זה כראי זה ולא ראי זה כראי זה הצד השוה שבהן שקונין בעלמא וקונין כאן אף אני אביא וכו'. ולפעמים כי לא אתי חדא מתרתי מייתי חדא מתלת ודוגמתו התם נמי ובכל דוכתא וקל להבין הוא ואין צורך באריכות

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