Medieval Theory of Vision

This post may have relevance to a book I am working on, so if anyone has any ideas or comments or explanations I would very much welcome them.

The ancient Greeks were basically divided into two camps of how vision works. One camp held with the theory of Emission (or extramission) in which visual perception comes from light beams which come out of the eyes. This view was held by Socrates, Plato and many others.

The opposing view held that miniature replicas of objects entered into the eye. This is the intromission theory and was an opinion held by Aristotle, Galen and others. These miniature replicas were called eidola and somehow represented the 'spirit' of the object being viewed.

(In fact there are another couple of theories which are kind of sub-categories of these, but I'm not knowledgable enough to explain the distinctions fully. Here are a couple of interesting articles that I found.

It seems to me that there are several examples in the Gemara which appear to side with the first opinion, that sight comes from light emmitted by the eyes.

For example:
The verse referring to Elisha states (II Melachim 2:24)

וַיִּפֶן אַחֲרָיו וַיִּרְאֵם, וַיְקַלְלֵם בְּשֵׁם יְהוָה; וַתֵּצֶאנָה שְׁתַּיִם דֻּבִּים, מִן-הַיַּעַר, וַתְּבַקַּעְנָה מֵהֶם, אַרְבָּעִים וּשְׁנֵי יְלָדִים.

And he looked behind him and saw them, and cursed them in the name of the LORD. And there came forth two she-bears out of the wood, and tore forty and two children of them

The Gemara explains this in Sotah (46a), stating:

מה ראה אמר רב ראה ממש כדתניא רבן שמעון בן גמליאל אומר כל מקום שנתנו חכמים עיניהם או מיתה או עוני

And he looked behind him and saw them, and cursed them in the name of the Lord. What did he see? — Rab said: He actually looked upon them, as it has been taught: Rabban Simeon b. Gamaliel says: Wherever the Sages set their eyes there is either death or calamity

In other words, it seems that sight has power to cause damage. This source is not conclusive, but how about the story of Rabbi Shimon Bar Yochai when he and his son came out of the cave (Shabbat 33b):

נפקו חזו אינשי דקא כרבי וזרעי אמר מניחין חיי עולם ועוסקין בחיי שעה כל מקום שנותנין עיניהן מיד נשרף

So they emerged. Seeing a man ploughing and sowing, they exclaimed, 'They forsake life eternal and engage in life temporal!' Whatever they cast their eyes upon was immediately burnt up.

Similarly, when Rabbi Shimon saw Yehuda ben Gerim, who was the one who informed the Romans of his words the Gemara says (ibid. 34a)

נפק לשוקא חזייה ליהודה בן גרים אמר עדיין יש לזה בעולם נתן בו עיניו ועשהו גל של עצמות:

Then he went out into the street and saw Judah, the son of proselytes: 'That man is still in the world!' he exclaimed. He cast his eyes upon him and he became8 a heap of bones.

It seems that according to Chazal there is a fire that comes out of the eyes, which is normally weak, but when coupled with strong spiritual force it can become an actual fire and burn things up.

The truth is that I understand that the concept of ayin hara is also based on this worldview. I know that nowadays we tend to explain it as based on jealousy of others, but if so, why is there no concept of 'ozen hara'? It seems that actually looking at something has power to cause damage. Conversely there is a saying that:

וא"ר יצחק אין הברכה מצוייה אלא בדבר הסמוי מן העין

R. Isaac also said: A blessing is found only in what is hidden from the eye, for it is written, The Lord shall command the blessing upon thee in thy hidden things. The School of R. Ishmael taught: A blessing comes only to that over which the eye has no power, for it is said, The Lord shall command the blessing upon thee in thy hidden things.

All of these sources imply (to me) that the eye emits some force which can cause physical damage if not channeled properly.

(I know that Superman had similar powers - where do you think he got the idea from?)

Rashi in Chumash is explicit that this is how sight works. In parshat Haazinu (Devarim 32:10) the verse states:

יִמְצָאֵהוּ בְּאֶרֶץ מִדְבָּר וּבְתֹהוּ יְלֵל יְשִׁמֹן יְסֹבְבֶנְהוּ יְבוֹנְנֵהוּ יִצְּרֶנְהוּ כְּאִישׁוֹן עֵינוֹ

He found them in a desert land, and in a desolate, howling wasteland. He encompassed them and bestowed understanding upon them; He protected them as the pupil of His eye.

Rashi explains:

"כאישון עינו" - הוא השחור שבעין שהמאור יוצא הימנו"

as the pupil of his eye: This refers to the black part of the eye, from which the light comes outward.

I haven't yet found the source of Rashi's statement in Chazal. Perhaps one of you knows whether Rashi took this explanation from an earlier source, or it is his own chidush. Also I have looked, but not yet found, whether any of the commentaries on Rashi manage to explain this in accordance with modern theories of sight (i.e. that light comes from a light-source, is reflected off objects, and then enters the eye).

And what is also interesting is that both Rabbeinu Bachye (on the verse) and Meiri (in his commentary on Tehillim 17) seem to side with the other theory of sight, and say that the word ishun means pupil because of the 'little man' (ish) that can be seen within it. This seems to be the theory of eidola, that reflections leave the object and enter the eye. Again, I cannot find a source in Chazal for their commentary, but I would be glad if someone could find one for me.

It apears that the modern theory of sight first developed in the end of the 10th century and beginning of the 11th by Abu Ali Mohammed Ibn Al Hasn Ibn Al Haytham, whom we know today as Alhazen. However, since he lived mainly in Cairo, and wrote in Arabic, his works would have been unknown to Rashi, Rabbeinu Bachya or Meiri. But they should have been known to those who came not much later. Which is why I would expect later commentaries on Rashi (particularly) to explain him according to the 'modern theory.'

Invalidating a Beit Din

Over on CrossCurrents Rabbi Gordimer continues to accuse Rabbi Zev Farber of heresy. (To be honest, I'm not sure that he is wrong - it seems to me that Rav Farber has crossed some unwritten line, but that may be the topic of another post). However, in his latest post Rabbi Gordimer goes a step further. He writes:

The beliefs of a rabbi are no small issue. They can impact the validity of geirus, gittin and kiddushin performed under the rabbi’s review or that hinge upon his testimony, and the halachic integrity of those institutions that affiliate with a rabbi whose beliefs are unacceptable becomes suspect.

In other words, not only would any conversions, divorces or marriages performed by Rav Farber be invalid, but by association, any of those performed by anyone affiliated with YCT (Yeshivat Chovevei Torah - Rabbi Farber's alma mater) would also be invalid. I find this claim very disturbing.

Firstly, and obviously, I don't know why a marriage would be invalid, even if performed by a heretic. One does not require a Rabbi to perform a wedding.

But aside from that, to invalidate an entire institution based on the writings or thought of one individual sounds like a very dangerous precedent (not to mention that YCT have distanced themselves from Rabbi Farber's views, and stated openly that his views do not represent those of the school).

The kinds of sins which invalidate dayanim are (according to Shulchan Aruch) those that invalidate witnesses.
In Choshen Mishpat, siman 32 se'if 22 it states:

המוסרים לאנסים, והאפיקורסים והמומרים לעבודת כוכבים, פחותים מהעובדי כוכבים ופסולים לעדות.

those who hand over [Jews] to the secular authorities, and apikorsim (heretics) and those who are known to worship idols, are less valid than idolators, and are invalid as witnesses.

If it were to be decided that Rav Farber was an apikoros, he would be invalid as a judge (and witness) based on this halacha.

But if we look earlier in the siman, and the much longer discussion of other kinds of sins which invalidate judges (and witnesses) we find:

גנב, וכן גזלן, פסולים לעדות מעת שגנב או גזל, ואע"פ שהחזירו, עד שיעשו תשובה.

A thief or a robber are invalide for testimony from the moment they stole or robbed. Even if they return [the money they are still invalide] until they repent

Imagine, hypothetically, that a chief Rabbi of Israel would be indicted for fraud, bribery, money laundering and theft. If he were to be convicted, would that invalidate not only any beit din that he personally had sat on, but also every beit din under his jurisdiction? Were he to be found guilty, even if he repaid the money, would every divorce performed in Israel for the past several years be invalid? And how about every conversion? It would undermine the very fabric of society. (I'm not accusing anyone, nor do I think that anyone is guilty. This is a hypothetical question based on Rabbi Gordimer's assumption that any Beit Din associated with an individual Rabbi should be tarred with the same brush as an individual. This case would be worse, because the accused is the head of the organisation).

Or, Rambam writes in Hilchot Eidut, chapter 17 halacha 1

יז,א מי שהעידו לו אנשים רבים וגדולים בחכמה וביראה, שהם ראו פלוני שעבר עבירה פלונית, או שלווה מפלוני--אף על פי שהוא מאמין הדבר בליבו כאילו ראהו--לא יעיד, עד שיראה הדבר בעיניו, או יודה לו הלווה מפיו ויאמר לו, היה עליי עד: שנאמר "או ראה או ידע" (ויקרא ה,א). ואין לך עדות שמתקיימת בראייה או בידיעה, אלא עדות ממון. וכל המעיד מפי אחרים--הרי זה עד שקר, ועובר בלא תעשה: שנאמר "לא תענה בריעך עד שקר" (שמות כ,יב).

Someone to whom many people who are great in wisdom and fear of G-d, have testified that they saw someone transgress a sin... may not testify unless he sees it with his own eyes... Anyone who testifies based on the testimony of others is a false witness and transgresses the negative prohibition of "do not bear false witness agsinst your neighbour

Now imagine, hypothetically, that the head of a very large Rabbinic organisation in America was defending a convicted criminal based on evidence he had heard from others, and his own 'investigation' (this is not exactly the same as Rambam's halacha but pretty similar). Imagine if the Rabbi continued to insist on his innocence even after the criminal had confessed and pled guilty and been sentenced to jail. Furthermore, this Rabbi accused someone else of perpetrating the crime, with no evidence. And he continued to insist that he is correct and refused to retract either his claim of innocence on the confessed perpetrator, nor his unfounded allegations against an innocent party. (I am not saying that this is what happened - I have no evidence apart from what I've read and heard from others, but I am suggesting a hypothetical case).

Would Rabbi Gordimer then invalidate any gittin or geirus done under the auspices of this organisation?

These are two hypothetical examples that come to mind. There are (unfortunately) many cases of financial crimes, or other sins which would brand someone a 'rasha' which have been perpetrated by Rabbis and Dayanim. If we were to follow Rabbi Gordimer's lead and invalidate any action performed by any Beit Din associated with them it would be extremely difficult to find any Beit Din in the world that is kosher.

To repeat: I am not accusing anyone of guilt (or innocence). I do not know whether Rabbi Farber is a heretic or not (nor is my opinion relevant). And I do not know whether Rabbi Farber actually sits on a Beit Din or not, and what the status of that Beit Din will be in the future. I am simply pointing out that if Rabbi Gordimer is correct (and I haven't claimed that he is wrong) we will need to review the entire system of Beit Din within every Jewish community and every country, to ensure it meets the rigorous (minimum) standards of not being in any way associated with anyone who is invalid as a judge or witness. Not that is a tall order!

New Chief Rabbis

I just wanted to write a very quick blog post about the newly elected Chief Rabbis - Rabbi David Lau and Rabbi Yitzchak Yosef.


Firstly, I am so glad that the elections are over. It has been an embarrassing chilul Hashem for the past several months as Rabbi engaged in politics and horse-trading. It should never have happened.

On the radio (and internet) this morning people were speaking about the election of chareidim as a defeat for the dati le'umi community, and a clear sign that the rabbanut does not want to move forward into the 21st century.

My thoughts (for what they are worth).

I do not identify with the chareidi community. But I do think that these two choices are excellent for Israel. Even though their fathers' were also Chief Rabbis, each of them deserves it in their own right, and was not elected because of their father.

I know Rabbi Lau a little bit (my brother knows him much better because he lives in Modi'in). Rabbi Lau is open, modern and concerned with the welfare of all Jews (and non-Jews) of every denomination. Notwithstanding what is being written about him, he cares deeply about people, knows Torah and halacha, and has been a tireless worker for the people of Modi'in for the past several years.

I know nothing about Rabbi Yosef as a person, but his books of Yalkut Yosef are tremendous. Clearly written, straight forward halacha for both Sefardim and Ashkenazim, and never erring on the side of chumra.

But as pleased as I am for both of these Rabbis, the Rabbanut and the State of Israel, I must say that it wasn't as much that these two won, but that the opposition lost. It seems to me that Bayit Yehudi is out of touch with the real world (based on the candidates they put forward). Rabbi David Stav is a forward thinking person (who wears a kippa seruga). But he has been exceptionally controversial in his rulings and actions (in terms of challenging the status quo). I think that Tzohar is an excellent organisation and has changed the way things are done. But to put forward such a radical contender for the office of Chief Rabbi was always risky. Tzohar operates well because it is outside of the system. I am yet to be convinced that it would work as the system.

And Rav Shmuel Eliyahu, who I'm sure is a great talmid chacham (though I have not been completely impressed with his halachic rulings on the weekly parsha pages, nor when I've heard him on the radio) and a great activist for the Jews of the world, is nevertheless a very controversial character. I disagree with the legal system getting involved in the elections - the Attorney General should never have allowed him to be called in - but nonetheless, his election would have been dragged through the courts and would have created an even bigger chilul Hashem. And those who feel disenfranchised by the election of Chareidim are possibly also the ones who would feel disenfrachised by a Rabbi who wrote a haskama to a book advocating killing Arabs.

If the dati le'umi community want to put up a serious contender for Chief Rabbi (and they should start planning now for 10 years time) they will have to find someone who is very knowledgable in Halacha, is not too radical, and can be accepted by most of the Jewish people of Israel. In the past they have had Chief Rabbis who filled most of those criteria - Rabbi Shapiro, Rabbi Mordechai Eliyahu, Rabbi Goren, etc. At the moment I don't see those kinds of people leading the dati le'umi community. Don't get me wrong - there are many great dati le'umi Rabbis, but many of them are either more chareidi than the chareidim, or radical in either their political or racial views.

Ten years is not a long time. They had better get moving. (Of course what they will probably do is change the electoral system or do away with the office of Chief Rabbi - which would be a pity, but more importantly would be an admission that they cannot compete on a level playing field.

Biblical Kangaroos

This post is inspired by the scientific writings of Dr Isaac Betech (pediatrician).

The statement by YSO that Kangaroos were known by both the Torah and by Chazal confused me at first, because it seemed to pose a difficulty to the mishna. But Baruch Hashem, using scientific methodology we have been able to clearly resolve all difficulties and show that Hashem is the Boreh Olam!

The mishna in Bikurim (2:7) states that:

דם מהלכי שתיים--שווה לדם בהמה, להכשיר את הזרעים; ודם השרץ, אין חייבין עליו.

The blood of those who go on 2 [legs] is equivalent to the blood of those who go on four [legs] to prepare plants [to enable them to beoome ritually impure]. And the blood of a sheretz [creepy crawly] - one is not liable for.

The strange phrase of 'go on two' is usually understood as referring to humans. However, kangaroos (and wallabies) also hop on two legs, thereby creating what at first seems an insurmountable difficulty.



We see from this video that kangaroos certainly 'go on two' [legs]. So one may have been misled to think that their blood is the same as human blood.

However, Baruch Hashem, a study of the meforshim (who all question why the mishna didn't simply use the word "man" rather than the less specific term "go on two") shows that they, know through their ruach hakodesh, of kangaroos.

Rishon le-Tziyon points out that from this wording one may have been confused and thought that it also included ofot. The word ofot is not clearly defined in Hebrew. It may refer to chicken (or turkey if you are American) or to birds in general.

However, I consulted with my Hebrew expert, who confirmed my suspicions, that the word עוף can also be read as "UP". This then, is clearly a reference to kangaroos who jump "up" when they move (unlike birds, for example, who simply fly). Therefore the mishna is precise in its terminology of saying 'go on two' to exclude kangaroos (and wallabies) who go 'up'.

R. Slifkin (R. stands for Natan) challenged that kangaroos were unknown to the audience of the Torah and the mishna. Which is not only irrelevant, but also false. Since the Torah and mishna were written with Divine Inspiration it makes no difference where they lived. Furthermore, only a small fraction of the land of Eretz Yisroel has been excavated for fossils, so it is entirely reasonable to assume that they will eventually discover kangaroo (and wallaby) fossils in Israel. Furthermore, I wrote a letter to the author of the book on kangaroos of the biblical era, and questioned his/her methodology. Since I heard no further response I assume that they agree with me that one cannot disprove the existence of kangaroos in the ancient Middle East.

In addition, anyone who goes to the Jerusalem zoo will see that there are both wallabies and kangaroos there. So it is false to say that there are no kangaroos in Israel!

Perhaps you will ask "What about gorillas? - They also walk on 2 legs". To which I answer that there is not a shred of evidence that gorillas walk on two legs.



Just two further points about Dr Betech:

1. He admits that he was involved in the ban on (Rabbi) Slifkins books.

The Chofetz Chaim (Hilchot Lashon HaRa 5:3) writes that one who says about a Rav that he does not know Torah and thereby causes his status to be diminished (and potentially causes him loss of livelihood) denigrates Torah and causes laxity in observance of mitzvot.

2. In his book, Betech fails to mention Rabbi Slifkin's book on the subject at all, even though he has certainly read it and is very familiar with it (and seems to have taken some of his sources from it). Furthermore, when a Rabbi says something that Betech does not agree with he either excludes it completely (like the opinon of Rabbi Tendler) or instead attributes Rabbi Lubin's opinionto a random parsha sheet (North Hendon Adath) to avoid presenting a difficulty to his theory.

Nodeh Be'Yehuda (Tanina: Orech Chaim 20) writes that one who fails to attribute a source (b'shem omro) is considered a thief and transgresses a Biblical command.
(disclosure: I found this reference in she'arim metzuyanim be'halacha siman 27, along with many other sources who state the same thing).

So in summary, one who denigrates a Rabbi and claims that he is not intelligent denigrates the Torah and causes people to be lax in their mitzva observance. Furthermore one who does not attribute their source transgresses a Biblical prohibition.


I'll end with a quote from Rebecca Driver:

Kangaroos are ingenious examples of God’s craftsmanship, designed by a Creator who knew perfectly what He was doing. To Him all praise, glory, and honour is forever due.