Wednesday, March 24, 2010

The Evolution of the Olive

Since olives are very small, how did it happen that the shiur of a kezayis got to be so big? That is the subject of my essay "The Evolution of the Olive," which you can download here.

In posting this essay, I am experimenting with a new model for publishing, based on the "donationware" model that exists with computer programs. I would like to make my writings accessible to the wider public, which does not happen if they are published in journals (unless it's Hakirah, which makes their archives available online for free, but I already have articles reserved for them). In addition, if I am going to devote extensive amounts of time to writing, I need to make it a viable source of parnasah. While I hope to eventually publish all my articles in book form, that is a difficult and very slow process, and it's a pity to keep it all locked up until then if there is another way to make it available. So I am posting this essay here, and asking that if people find they have benefited from my website in general and from this essay in particular, please make a modest donation using the button below. Thank you, and enjoy the essay!


  1. Well done! Excellent, thorough, research, presented very accesibly without sacrificing any substance or tracability of sources.

    I made a [truly] modest donation. Please continue to put these donation links on your essays.

    In the section on justifications for following contemporary-olive opinions, I might add that there are Halachic motivations that make being "stringent" to have a larger kezayit into being lenient on other things. You mentioned achila gasa above. In addition, there is a time limit on eating matza at the seder, and gargantuan kezayit standards could cause some people to miss the deadline. (Of course how long that is is another whole discussion.)

    So nu, R' Slifkin, how much matza are you going to eat for motzi matza?

  2. Very interesting. Thank you for sharing.

    I think another key point is what you mentioned in the beginning of the essay, but you did not elaborate upon.

    There is no “eating” with less than a kezayis (equivalent to an olive). (Toras Kohanim, Acharei
    12:2; Emor 4:16)

    It is inconceivable to me that chazal would say that there is "no eating" unless you eat an entire matza! That is not an "eating", that is a entire meal!

    (I hope many others take advantage of the donate button)

  3. Excellent article. Thank you very much. I am now better informed and will not drive myself crazy to eat a half a handmade matzah for a kezayis. Your article is also extremely relevant when dealing with older people,

    (By the way, I believe Rav Bar Hayim of Machon Shilo agrees with you.)

  4. Excellent as always. The only issue which I did not see discussed was the fact that a smaller shiur for a kezayit also leads to chumrot, such as eating food without a bracha acharonah and eating 'shiurim' on fast days.
    Is the Chazon Ish's large amma measurement related to his 'niskatnu habeitzim' theory?
    I heard a shiur from R. Mordechai Willig (available on, in which he pointed out, in partial resolution of the Tzlach's problem, that the thumb measurement is 'cubed', and with such a number, even a small difference ends up leading to a large one. Thus 4 cubed is 16, whereas 5 cubed is 25; thus a small difference in thumb measurement ratios will end up with a big difference in kezayis volumes. Additionally, Rav Willig argued that one can certainly rely on the contemporary olive measurement for the second kezayis that one is supposed to eat for motzi matza - thus one is supposed to eat 1/3 of a machine matza or 1/5 of a hand matza (if one does not totally accept that a kezayis is the size of a contemporary olive).

  5. A couple of typos you should correct.
    DaSilva rather than DeSilo, and Petrover rather than Futruver. You got these right in some places but not always. Also, I think it's Tufik rather than Topik. Also, Avraham Greenfield whose articles you refer to has recently published an entire sefer on shiurim that you may want to look at.

  6. Yisrael:
    I would be interested to know more about Prof Greenfield's new sefer, given that his approach is the most convincing I have seen.

  7. Frazzled from cleaningMarch 24, 2010 at 10:55 PM

    You mean if there's an contemporary-olive-sized piece of chametz somewhere in my kids' toybox I'm violating Bal Yeraeh? Same problem if there are a bunch of crumbs that add up to a kezayis! Aaaaaaa! I'd rather eat more matza by the seder!

  8. Very nice. One thing is that your interpritation of the yerushalmi is not the only one. From what I remember when I learned it, the implication is that Hashem gave the elders/beis-din/sanhedrin the authority to determine the minimmum biblical shiur. Therefore the kezayis issue boils down to whether or not near-universal acceptance of a shiur in halachah is equivalent to a uling by the sanhedrin. If so, then we are biblically obligated in teh alrger shiur, if not then we could use the "real" shiur.

    Since I dont believe there can be a definite ruling on that status, and since it is biblical, I think the accepted shiur should be practiced (that is, until enough people take the risk annd use the smaller shiur, thus re-ruling the original shiur due to lack of universal acceptance).

  9. I was going to make a quip about "The Evolution of the Olive", saying something about how the olive was actually created, but I decided not to. (smirk)

    Nice essay, R' Slifkin!

  10. lawrence kaplan

    Great Article. A better title would be, "The Alleged Evolution of the Olive."

  11. I didn't read it yet but you got my $17.99...

  12. 1. In what edition is the Tzlach on Pesachim 120a? In those I saw it's on "קי"ו ע"ב", that is קטז.

    2. It would be interesting to quote R' Elazar Fleckeles in Teshuva MeAhava, saying that his rabbi and master (R"Y Landau) was one of the tallest people he saw, and that he measured his own fingers.

    3. The Gemara in Pesachim says "Etzbah". You translate that as "Thumbs". The real translation is "fingerbreadth".

    I know the mefarshim say it is a thumb, but that shouldn't change the translation.

    4. The mishna says that jewish and roman measurements were interchangeable. The roman fingerbreadth (digitus) is believed to be cca 18.5mm.

    That would give us a revi'is of cca 68cc and egg of cca 45cc. Not impossible.

  13. Joseph: your mathematical point is even stronger than you realize because you computed squares. 4 cubed is 64, while 5 cubed is 125!

  14. It seems pretty clear that people today are taller than the people of several hundred years ago, but that doesn't necessarily mean that there is a steady graph upwards. The people of thousands of years ago may have been ever taller/bigger than nowadays.

  15. No, they weren't. There is such a thing as archeology!

    1. Some rather large skeletons have been uncovered over the years:

  16. David:
    The name of Prof. Greenfield's book is "Midah Keneged Midah," same as his article in Moriah.

  17. Yisrael:

    Now that i know its name, could you tell me a bit more about the sefer?

  18. Haven't read the article yet, but a preemptive remark: I believe R' Hirsch also weighs in on this as published in Shemesh Marpei. I don't normally do blog-related activities at home, so I doubt I'll ever think to post a page number :( but I'll throw it out there anyway.

  19. Rav David Bar-Hayim of Machon Shilo definitely agrees that a k'zayit is the size of an olive. Rav Bar-Hayim says that since this is the case one is yotzei if one eats 5 grams of machine matzah on layl haseder.

  20. David:

    A collection of sixteen articles he has published on the subject in various journals. 319 pp.

  21. Sighted at

    To determine the exact size of Torah olives, I went to the verse, "A Land of wheat, barley and wine, pomegranet, a Land of olive oil and honey".

    It occurred to me that this posuk lists the seven species IN SIZE ORDER! The posuk starts with the tiny grains are wheat and oats, continues with the slightly larger grape, and then the even larger fig, whatever that is. Thus, the size of an olive comes out to be somewhere between that of a pomegranate and that of a large jar of honey. Being that achilas matzoh is a mitzvoh me'dioreysah, (a commandment from the Torah) we must be machmir (stringent) by using the size of the jar of honey.

    After checking with officials at the Golden Blossom company, it turns out that the largest jar of honey sold commercially is 32 oz. So, by taking into account the amount of flour that fits into a 32 oz. jar, we come up with the shiur kezayis as being 4.7 round matzohs, or 6.4 square matzohs. Please remember that this matzoh must be consumed within the allowed time of 5 minutes!

  22. What I find interesting is that the species of bird whose egg is used in measurements is not mentioned in the gemara. R. Slifkin, were jungle fowl or similar species in use by Jews in Eretz Yisroel of those earlier eras? Or, were the most common bird and eggs consumed perhaps pigeons, doves or quail? If so, it's well known that the eggs of those birds are significantly smaller than chicken eggs. Would this fact have any bearing upon the size of a Beitza or Kezayit?

  23. While we now have one Biblical commandment to eat a K'sayis Matzoh, there are many Biblical prohibitions that are based upon the same measurement. While less than a full measure is still prohibited, the major violation whether for Malkus or Misah or Kares or for the obligation of bringing a sin offering are only achieved with a full K'sayis. Hence, the larger measurements are generally a leniency!!!

    Josh from Dallas

  24. As a follower of Rabbi David Bar-Hayim I would like to commend this research which contributes towards a more truthful Judaism (and a more enjoyable seder).

  25. A wonderful essay.

    What is striking, and disturbing, is the Chelm-like thinking that sometimes characterizes the halachic process.

    Incorrect observations, coupled with invalid (yet internally consistent) logic leads to blatantly false conclusions.

  26. David: the Gemara (Yoma 80a) specifically names a chicken egg as the beitzah used for halachic measurements.

  27. Prof. Greenfield also has a calculation of the amount of gold in the Mishkan which can be used to get the shiur of cubit and "olive".

  28. You made my Pesach much more enjoyable. 1) I never understood how kizayit wasn't a kizayit, and worse how none of the measurements made any sense as they taught me in Yeshiva. 2) I didn't feel like I failed to be yotzei in the mitzvah by not stuffing my face within the allotted time.

    Now could you discuss the proper measurements for wine?

  29. Responsum of R' S.R. Hirsch
    Shemesh Marpei, Orah Hayim, Siman 23
    Translated from Hebrew by yitznewton

    Tuesday of Ki Savo, 5644 (September 2, 1884)
    [In response to R' Pinchas Elchanan Wechsler of Schwabach, regarding how to render Torah measurements in centimeters]

    [R' Hirsch first apologizes that he was forced to limit his research and response due to the state of his health]

    In my humble opinion there is no doubt that you have done according to Torah law in seeking a mean fingerbreadth between the largest and smallest man's [finger] found among you. If you establish this value to calculate the practical Torah measurements that you come upon [including] the size of the lechi of your city's eruv, there is no doubt that you have discharged your obligation, for you will have done that which is incumbent on you in Torah law. There is also no doubt, in my humble opinion, that you should not be surprised if other Rabbis elsewhere will not [have the same value as] yours, with one rather being less and another greater than your measurement.
    For to my limited knowledge, it is totally impossible to definitively establish a single universal value for the measurements of the Torah's laws, and the Blessed Giver of our Torah did not have this in mind at all. Are not all the Torah's measurements essentially the dimensions of fruits and parts of the body: olive, pomegranate, barley-corn, kotevet, egg, fingerbreadth, handbreadth, cubit, etc.; and the size of fruits and the stature of people, on which these measurements are based, differ in every place and generation. So perforce there will be varying values for the measurements of the Torah. In my humble opinion this does not reduce the truth of the Torah but rather increases it, for the goal of all of the Torah's laws is only to straighten human affairs. The basis for all their measurements as given to us is, in my humble opinion, בערך מה אל ענין א' מעניני בני אדם. For example, in my humble opinion it is quite likely that the measurement given for the height of a mehitzah, whose purpose is to delineate human domains, will be larger or smaller according to the the height of the average person in a given time and place. I cannot elaborate, and anyway there is no need for an understanding person such as yourself. Also, even in a single time and place, fruits and people are not identical in size, and it is all but impossible that all who measure will find precisely the same average. [...]

    [R' Hirsch goes on to recall a history of having local official shiurim, and advocates this]

    (I didn't understand the bit I quoted in Hebrew; cheers to anyone who does and can translate it)

  30. Thank you for posting the article. I found it quite informative and I hope you will do more like that in the future. I do wish, though, that you had explained the basis the Nodah B'Yehudah's opinion using thumb-breadths more fully.

  31. Thanks for the article. The kezayit is a touchy issue every year at our family's seder, when those present of the older generation feel slighted when they see that how they always ate matzah is “no longer good enough.”

    I have to recommend R. Haym Soloveitchik's article, “Rupture and Reconstruction: The Transformation of Contemporary Orthodoxy,” from Tradition, Summer 1994. He writes that the stringency regarding the shiur of matzah became widespread in the 1940s and 50s, and he presents it as a paradigm of the sociological changes that happened in his generation of Orthodoxy. The article is available online here. (He also comments on the divide in the haredi world over cosmology that R' Slifkin brought to the open ten years later.)

  32. A simple and practical הלכה למעשה article on שיעור כזית מצה can be found here:

  33. But it has a giant shiur kezayis! That's not very simple or practical...

  34. If the two sugyot in the gemara say that a throat can hold two olives or one egg, i don't see how this implies that the *volume* of an olive is half that of an egg. I would think that the limiting dimension is the diameter of the cross-section of the esophagus; thus the *diameter* of an olive would be one-half that of an egg (which is reasonable given our olives and eggs) and you'd have to *cube* that linear ratio to get the ratio of volumes. And 1:8 is pretty close to the Ritva's 1:9.

  35. Rabbi Slifkin, an excellent set of arguments. But I would disagree with one of your initial premises. You say that logically in order to reach the conclusion that a kezayis is much larger than olives are
    today, two separate positions must both be taken- both that ancient olives were larger and secondly that we must follow them.
    I suggest this is a false dichotomy.
    It is possible to say that a kezayis the much larger size that is widely held today simply because even if it was a tremendous mistake (which seems likely) it was widely adopted as minhag and therefore by dint of it being adopted as minhag, that is sufficient to render it as the halachically prescribed size.

  36. Great article ! I paid and i didn't regret ! ישר כוח

  37. Nice article. I don't know if you're aware but apparently Rabbi Dov Lior, who is currently in the news, paskens that a kzayit is the size of a regular olive.

  38. Perhaps this is a minor nit-pick, but I will offer it nevertheless:

    You state that an amphora is equal to a cubic Roman foot which is 25.79 liters. First of all, if you google it, you will find that though this may be accurate in theory, opinions offered for modius (1/3 of an amphora) range from 8.5 to roughly 9.3 liters. Therefore Greenfield's 43 cc for a beitzah easily fits into this range.

    Second of all, your calculation is off. A Roman foot is 2/3 of an amah. A Roman amah is 44.4 cm. Therefore foot =29.6. 29.6^3=25.934 liters per amphora. Modius = 8.644 liters. Egg = (@217) 39.84, or(@207) 41.76.

    I am not sure what you mean by rationalist Judaism, but this issue has nothing to do with rationalism or whatever its opposite is.

  39. R Slifkin,
    Are you aware that Kislev translates weight for volume in his article. He wrote that since the specific density of olives are about 1, that there is no problem. I am sure the difference does not amount to a k'zayit of even 19 ml but in my opinion it is not good research.
    Noam Kaplan

  40. Over Pesach I read Rabbi Slifkin’s paper on The Evolution of the Olive. Towards the end, Rabbi Slifkin says: “contemporary halachic authorities are emphatic that the kezays is to be measured by volume, not weight.” Later, in footnote 69, he brings a number of sources and among those sources he quotes R. Ovadia Yosef, Chazon Ovadiah, vol II p.518.

    When I read the paper I was in shul so I did not have access to my Chazon Ovadia, but I was sure that the quote was not correct. In fact, being a Sephardi Rabbi myself, I knew with certainty that R. Ovadia emphatic position is that the Kezayt must be measured in weight and not by volume.

    It is true that the quote from Chazon Ovadia at the beginning says that many authorities say that the Kezayt has to be measured by volume, but then R.Ovadia says that ever since it has been established that the size of the Kezayt is in comperasion with the Egg and the Drahm, therefore, today we have to measure the Kezayt by weight.
    R. Ovadia brings the same Psak in Chazon Ovadia Hagada shel Pesach page 41 where he clearly says that the measure of the Kezayt has to be measured by weight (minimum of 18 gr to 27 gr lechatechila). The same Psak is also brought in Yalkut Yosef – Moadim.
    To be clear, this message in no way intends to undermine Slifkin’s efforts. Merely to bring to his attention one flaw, so as to bolster his argument.
    Rabbi Michael Beyo

  41. As regards to Rabbi Beyo's comment:

    Given 8 hand matzot per lb, Rav Ovadia's c'zayit is as much as 1/2 of a hand matza. (400 grams/8 = 50 gram per matza).

    Olives range from 2-7 grams in weight, according to the following site.

    As Sepharadim always knew what an olive looked like, I therefore do not understand why Rav Ovadia would say an olive's weight is 18-27 grams.

  42. Re. David's last comment:

    According to the following site, modern green olives are generally grouped into grades ranging from 3.2 to 16.2 grams:

  43. This comment is a little late in the piece but...
    I have read the monologue and was impressed. One thing did jump out at me though.

    The textual interpretations required by the Ashkenazi rabbonim due to not having actual olives at hand seem to begin with alignments of the three gemorohs mentioned by R. Slifkin that imply different olive sizes when related:

    Gemoroh a. Two olives fit in the throat
    Gemoroh b. An egg fits in the throat
    Gemoroh c. A dried fig (bigger than an olive) is less than a third of an egg.

    R. Slifkin mentioned that equating a and b imply an olive seems to be half an eggs volume, while c implies that an olive is considerably smaller than a third of an egg. He mentions that some resolve the contradiction by working to explain a and b to come to a different conclusion than half an egg (e.g. the difference between comfortably fitting and struggling to fit an object down the throat).

    Those who chose to uphold the primacy of the comparison of a and b ended up pushing for an olive that compared in volume to half an egg and thus began the whole (mis)calculations that get us to this point in time where a kazayit is impressively non olive like.

    Sorry for the above summary. I do have a point I am trying to get to. It seems to me that there is a very simple way of understanding the three sources that seems most logical and provides a conclusion that all three gemorohs were under the impression that an olive was actually much smaller than a third of an egg (like in reality).

    It comes down to understanding the physical nature of what is being discussed in Gemoroh a and b, the act of swalling round (I know – oval – but for mathematical simplicity round will do) objects.
    For simplicity, lets pretend that an olive and an egg are perfect spheres (simplifies the calculations).
    When swallowing these, the assumption is that the olives are going down together (next to each other). This gives the diameter of one olive to be equal to half of the diameter of an egg (what many rishonim used to give an olive as half the volume of an egg).

    Working back to volume (4/3*Pi*r^3), if the radius of the olive is for example 1, the radius of the egg is then 2, the volume of the olive is 4/3*Pi*1^3 so approximately 4.2 ccm. The volume of the egg is then 4/3*pi*2^3 so approximately 33.5 ccm (do you see where I am going with this). In ratio, the gemorohs a and b are really saying that an egg has a volume 8 times larger than an olive. This fits with reality and also fits with gemara c (smaller than a third of an egg) as well hence no contradiction in implied volumes.

    The conclusion does not differ from R. Slifkin’s. In many ways it is irrelevant as he clearly shows via gaonic sources that the intention was not to use eggs to calculate olives but rather step outside and take an olive as a guide. But, interesting nonetheless.

  44. @530nm330hz
    @Reuven Lewis
    closer examination of the Gemara in Krisos 14a will show that the gemara was not referring to swallowing actual olives, but to a piece of meat (Chelev) equal to the volume of 2 olives

  45. In this interview, R. Dovid Cohen says that based on archeological evidence, an olive is the size of an olive:

  46. Here is some source material that seems to have been overlooked to date.

    מנחות כ"ו:ב
    רבי יהושע בן לוי סבר אין קומץ פחות משני זיתים...ורבי יוחנן סבר יש קומץ פחות משני זיתים

    The Halakha follows R. Yehoshua Ben Levi. So a kezayit is half a kometz. I don't know about you, but although I can fit two olives inside my own kometz, I can't fit a whole egg inside my own kometz.

    1. The non-rationalists will counter that people were much bigger back then!

  47. Rav first thank you for all you do for us.
    Hakarat hatov.
    Does the evolution of the kezayit exist in Hebrew ?
    Be well.

  48. A very well-written responsum.
    Is the link to the article down?


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