In Chagiga 5b: Why aren't Rav Kahana's action taken to task by the gemora? Yes, he wants to learn from his teacher Rav . Yes, seeing a teacher practice what he has taught is great. Yet why doesn't Rav Kahana take into account other things he must have learned, e.g. the privacy between husband and wife; that at a chasena one is not even allowed to comtemplate the culmination of the event; Since your teacher is likened to your father, isn't this like uncovering the nakedness of your father in a manner of speaking? It seems so unthinkable one wonders why the gemora even included this.
First, it should be pointed out that in fact the relationship between Rav and Rav Kahana is not one of pure Rebbi/Talmid. This Rav Kahana was the first of five of that name, and he was a Talmid-Chaver (a colleague, as well as student) of Rav (see Sanhedrin 36b, and Nazir 19a, where he and Rav Asi asked a question to Rav, who treated Rav Kahana with deference; see, also, Shabbos 24b).
Second, the main Sugya is found in Berachos 62a, where similar incidents regarding conduct in the bathroom are reported about Rebbi Akiva with Rebbi Yehoshua, and Ben Azai with Rebbi Akiva. There, the Gemara records that Rav rebukes Rav Kahana, and Rav Kahana gets in the last words (omitted in Chagigah) and says, "Torah Hi v'Lilmod Ani Tzarich" -- "It is Torah, and I have to learn," as Ben Azai and Rebbi Yehoshua had said in the preceding incidents recorded there. It seems that the Torah-learning factor -- provided that it is absolutely sincere -- overrides that of Tzniyus. Even Rav, in his rebuke of Rav Kahana, did not reply that what he did was wrong, but only that it was not appropriate behavior in the circumstances: "Go out, for it is not Derech Eretz (proper manners)."
Third, there is no indication that Rav Kahana actually could see what was going on. He hid under the bed and heard the discussion between husband and wife, as the Gemara says.
Fourth, the source for the requirement for privacy in this matter is found in the Gemara in Nidah (16a and 17a) where Rebbi Shimon says that "there are four things that Hash-m despises, and for myself, I do not like them" (see the Maharsha there in Chidushei Agados, Hagahos Ya'avetz, and Aruch la'Ner to explain what Rebbi Shimon means), and one of those four things is "one who has relations in front of other persons." It is not stated there that it is prohibited , but only that it is not acceptable behavior. So, too, the TUR (OC 240) phrases it not as a prohibition, but as a positive duty to be modest. (The Shulchan Aruch OC 240:6, though, translates this into a prohibition.)
It is to be assumed, therefore, that Rav Kahana's presence there without the knowledge of Rav did not constitute an infringement by Rav of any negative prohibition nor any "Lifnei Iver" by Rav Kahana. As long as Rav was unaware of any other person being present, he was acting with full Tzniyus. Only later, when he did become aware that Rav Kahana was present, did it become contrary to Tzniyus and at that stage, Rav told him to get out, "for it is not Derech Eretz."
It is true that nowadays such conduct would be unthinkable as you ask, but that is because the level of sincerity in Torah learning has fallen tremendously since the days of the Amora'im (cf. Kesuvos 17a, where Rav Acha carried a Kalah upon his shoulders because he was capable of saying that she was nothing more than a beam of wood to him, whereas nowadays such conduct would be unthinkable). Rav Kahana, too, did not consider himself to be interfering with the rights of privacy of Rav, as his mind was completely, robotically, controlled by the dictates of the Torah and he was not contravening any precept, as we have explained.
The MAHARSHA in Berachos (62a) explains that not only was Rav Kahana's act not inappropriate, but to the contrary, Rav Kahana was conducting himself with the utmost modesty, in that he refrained from openly asking Rav about the matters between a man and his wife, for it is prohibited to speak about them openly.
Regarding your question why Rav Kahana was not punished for this, perhaps he was punished, for we find in Bava Kama (117a) that he was forced to flee from Bavel to Eretz Yisrael because of threats from the ruling party there, that came about through a strange incident (we also find that the two others, Rebbi Akiva and Ben Azai, who acted in this manner with their teachers, passed away in strange and unusual ways, Rebbi Akiva in Berachos 61b and Ben-Azai here in Chagigah 15b). Even though they knew that they might be punished, they still acted the way that they did because "it was Torah, and I must learn," as the Gemara mentions.
Mordecai Kornfeld
I think that the Rav Kahana mentioned in Bava Kama refers to the second Rav Kahana, a Talmid of Rav and Rebbi Yochanan, who was not a Kohen (as per Pesachim 49a and Chulin 132a, and see Kidushin 8a, Tosfos DH Rav Kahana, first answer (the second answer there, in any event, does not work according to the Rosh at the end of Bechoros)), not to the first Rav Kahana, about whom we are talking, who was a Kohen (see Pesachim 113a) and a contemporary Talmid/Chaver of Rav.
I found that the Maharsha in Bava Kama there writes explicitly that the incident there involves Rav Kahana the Talmid/Chaver of Rav.
Moreover, we can add that in the incident with Rebbi Akiva and Ben Azai in Maseches Berachos, they were questioned by their Talmidim, "Ad Kan he'Azta" -- "To such an extent you are so brazen?!" to which they responded, "It is Torah, and we must learn."
We find that both the death of Rebbi Akiva and the death of Ben Azai came about because of their strong and brazen love for the Torah, for Rebbi Akiva was so brazen as to teach Torah during the time of the Roman decree forbidding it, and Ben Azai brazenly enterred the realm of the Pardes for which he was not yet ready. We also find that at the time of the death of Rebbi Akiva, his Talmidim used a similar phrase as they used in the incident above, when they saw him calmly accept his torture and death and they said to him "Ad Kan" -- "To such an extent?!" (It is interesting to note also that both Rebbi Akiva and Ben Azai, out of their brazen love for the Torah, left their wives for the sake of learning and teaching Torah.)
-Mordecai
I note what you say from the Maharsha in Bava Kama (117a) and he does refer to the Gemara in the fourth Perek of Sanhedrin (which I assume means 36b) which implies that he holds it is the same Rav Kahana. However, this is clearly not so from Rashi in Bava Kama (117a, DH Lo) who says that this is Rav Kahana of Pesachim (49a) who was not a Kohen. So, too, from the Yerushalmi quoted by Rashi, it is clear that this Rav Kahana was much younger (see Yerushalmi Berachos 2:8, "Kahana was very young when he came up to here," and, as the Yerushalmi goes on to explain, he returned to Bavel afterwards. In contrast, Rav Kahana the first went up to Eretz Yisrael long before the death of Rav and he remained there and did not return to Bavel.)
See also Sefer Toldos Tana'im v'Amora'im, entry "Rav Kahana," which gives a very nice and lengthy explanation for all of this, as well as all of the details of these two Rav Kahanas.
However, what you wrote regarding Rebbi Akiva and Ben Azai was most interesting and perceptive.
b'Yididus v'Kol Tuv,
Joseph Pearlman
Yiyasher Koach Rav Kornfeld for the Divrei Torah-
Somethings I dont understand so I ask for clarification.
a) What was strange in the incident that forced R Kahana to leave Bavel. He
killed a man who was a moser and was advised by Rav to leave babel for his
own safety. In what way is that strange?
b) Where do we see that the Rebbeim of Rabbi Akiva and Ben Azai were against
what they had done with regard to their looking on in the Beis Hakisei. We
only find that the Talmidim asked if a talmid must even go so far with his
rebbe, not that the Rebbeim had shown displeasure with what they had done
(especially since Ben Azai himself followed R Akiva ( who at another occasion
followed R Yehoshua) into the bathroom and obviousely R Akiva wouldnt have
been nothered by that and would have understood the intention and the need to
learn as he himself followed R Yehoshua. . Only when R Kahana was under the
bed do we find that Rav Said Its not proper So why are we to assume that
there was something inherently wrong with following ones teacher into the
bathroom when the Gemarah seems to be satisfied with the response given by R
Akiva and Ben Azai respectively. Additionaly we dont see in the Gemarah that
Rav said anything negatively to Rav Kahane after he responded with Torah Hi
Vlilmod ani Tzarich. It is torah and I must learn it, rather he expressed
displeasure before R Kahana responded until he saw that R Kahanas
intentions were 100% pure.
c) Wasnt Ben Azai a Bachur and never married? Where do you find that he left
his wife to learn torah?
Thank you for your time.
Kol Tuv.
Yaakov Y. Fischer
a) Killing a man, and then being forced to flee because of the authorities, is considered a strange way to make Aliyah.
b) You are correct -- we do not see that their Rebbeim were displeased with their conduct, and we did not write as such. We merely suggested that there might have been a connection between their unusual deaths and their relatively unusual conduct of learning Torah by observing the private behavior of their teachers.
Your insight that Rav did not respond to Rav Kahana after he said "Torah Hi v'Lilmod Ani Tzarich" because he saw that Rav Kahana's intentions were absolutely pure, is very good. However, in Shamayim there might have been some element of impropriety in his actions (not that what he did was inherently wrong, but that for a Tzadik on his level it might have been considered improper), for which he might have required to receive rectification in this world.
c) We did not mean that he left his wife to learn Torah, for you are correct, he was never married. Rather, he left getting married (i.e. he never married) in order to learn Torah.
All the best!