Chatzi Hallel

There are basically 4 shitos on the issue of whether you make a bracha on chatzi hallel or not (for example - on Rosh Chodesh or the latter days of Pesach):

Shitas HaRambam: No bracha at all on chatzi hallel.

Shitas Rabbeinu Tam: One does make a bracha on chatzi hallel.

Shitas HaRaavad: On Rosh Chodesh you make a bracha and not on the latter days of Pesach.

Shitas HaRamban: On Rosh Chodesh you don't make a bracha and on the latter days of Pesach you do.

The Brisker Rav in Brachos 16:11 discusses this issue. Briefly, his basic premise is that one only makes a bracha on a cheftza shel mitzvah and the real machlokes is how exactly we define what is a cheftza shel mitzvah. Perhaps we will return to this issue in more depth another time.

The Machzor Vitri (page 192/siman 226) brings Rabbeinu Tam's shitah as well as some opposing views. Also, the Kol Bo in his halachos of Rosh Chodesh brings some shittos.

As far as why we say chatzi hallel on Rosh Chodesh, this comes from a gemara in Erchin 10b that no shira is needed if it isn't mekudash lechag. There is also a gemara in Taanis 28b that mentions that reciting hallel on Rosh Chodesh is a minhag. The gemara there relates this to the fact that the hallel is said bidilug.

Al Hanissim in Al Hamichya Part 4

I hate posting on the same thing over and over again... but I finally found the Brisker Rav's answer inside (see this earlier post). The Griz is, in fact, found in the back of the Griz Al HaTorah (as a commenter pointed out to me). Here is a rough translation of what the Griz has to say:

It needs investigation why we do not mention on Chanuka and Purim Al HaNissim in the Bracha Me'ein Shalosh. And it seems, because Al HaNissim has no "din bracha" on it, and it is only a mere hodaah, and in the bracha me'ein shalosh there is only room for a bracha, and for that reason we don't mention in it Al HaNissim. And that which we mention Retzai and Rosh Chodesh in the Me'ein Shalosh, we need to say that there is, in fact, a "din bracha" [on them]. And the proof of this is from that which we say in the gemara that if one forgets and doesn't say Retzai etc. he says after Bonei Yerushalayim and ends with a bracha, so you see that there is a din bracha, and it's not merely a hazkarah. And according to this it is also explained, that because the only reason that we mention Retzai in the bracha me'ein shalosh is only because it is a bracha, and since the whole din bracha of retzai is only after bonei yerushalayim, and that is when you forget to say it on shabbos in its right place, so therefore its place in the me'ein shalosh is after bonei yerushalayim, since the whole din bracha that it has is only after bonei yerushalayim. - Grach

I think that the answer given in that weekly torah publication that I posted here was taken from this Griz but written in an abbreviated fashion.

Eidi Mesirah/Chasima Karti 2

ז] כיצד בשטר: כתב לו על הנייר או על החרס או על העלה שדי נתונה לך, שדי מכורה לך--כיון שהגיע השטר לידו, קנה: ואף על פי שאין שם עדים כלל, ואף על פי שאין השטר שווה כלום

This Rambam is based on a baraisa in Kiddushin 26a. However, offhand the Rambam's lashon is strange. It sounds like if one uses a shtar to acquire land, the shtar works with no eidim whatsoever! We know there is a machlokes between R' Eliezer and R' Meir as to whether a shtar needs eidi chasimah or eidi mesirah (see this post), but nobody says a shtar works with no eidim at all?!

Tosafos in Gittin 22b (d"h Aval) understands the baraisa in Kiddushin as referring to a shtar with eidi mesirah, following the opinion of R' Eliezer. However, this runs into problems because the gemara in Gittin there says explicitly that one cannot write a shtar on a davar sheyachol l'hizdayef (i.e. on paper that can be erased and one can change the contents of the shtar) by other shtaros besides gittin, and rely on eidi mesirah to remember what the shtar said. This is learnt from a pasuk in Yirmiyah of "lmaan yaamdu yamim rabim", a general shtar has to be able to last "many years", even beyond the memories of the eidi mesirah. Tosafos therefore makes a distinction between shtaros that are made for raaya purposes and shtaros made for kinyan. Only shtaros specifically made for raayah purposes need to be able to last "many years". Shtaros made for kinyan, however, can even be written on davar sh'yachol l'hizdayef and one can rely on the eidi mesirah to remember.

[ By the way, the implication of Tosafos is that eidi mesirah work on shtarei raayah. This gets into the issue we mentioned here about R' Soloveitchik's yesod that eidi mesirah don't work on shtarei raayah. ]

Rabbi Schachter in Eretz HaTzvi (page 164) seems to learn the Rambam as dealing with a shtar with eidi chasimah. This really seems to run into a problem because the gemara in Gittin specifically does not allow eidi chasimah on davar sheyachol l'hizdayef. It's only by eidi mesirah that the possibility exists.

The Birchas Shmuel in Gittin 14:6 deals with this issue. He says that eidi chasimah in general create an anan sahadi that there was a proper mesirah. This anan sahadi works to create a shtar even in the face of the problem of yachol l'hizdayef. However, the anan sahadi cannot also create a gerushin in such a scenario. (The idea is that by gerushin the anan sahadi is needed both to create a shtar and to effect the gerushin because of the rule of ein davar shebervah pachos mishnayim. The second issue cannot be resolved by the anan sahadi in this case. Why should the first issue be resolvable and not the second? I don't see the answer to that in my notes. Check the Birchas Shmuel I guess.) See the Ktzos HaChoshen 42:1 regarding this issue as well.

Another problem arising with this approach in the Rambam is that the Rambam really paskens eidi mesirah karti. Why go with eidi chasimah here? One option would be to say that the Rambam only held eidi mesirah karti by gerushin to effect the divorce, but not to create the shtar. One needs to examine Gittin 86b and 22b to determine if this approach can work. There are other possible ways to get out of this question (again see this same post which opens the door to some of them).

The Uniqueness of Shtarei Erusin

The Gemara in Gittin 9a discusses a case where one frees an eved but "leaves over" something for himself within the shtar. For example, the shtar might say, "all my property is yours except...". In the hava amina of the gemara the issue is dependent upon the concept of palginan diburah (see the sugya itself for details). However, in the maskana, Rav Ashi comes up with an alternative reason why such shtaros are no good. Rav Ashi says, "here the reason why it is no good is because it's not a get that totally cuts off". The Rif (2b) explains that since in the shtar there exists some zchuyos to the adon the shtar isn't totally the property of the eved. The shtar used to free the eved has to contain 100% entitlement to the eved (see Rashi also for his explanation of krus gita).

R' Akiva Eiger asks on this idea of the Rif from a sugya in Gittin 40a where the case is that one frees a shifcha. The gemara says that one may give the shifcha a shtar that says "go free with this and marry me." In other words, the same shtar is functioning both to free the woman and marry her to the adon. The question is apparent. Doesn't this shtar contain an entitlement to the adon? How does the Rif understand this gemara?

R' Akiva Eiger answers by pointing out the uniqueness of shtarei erusin. All other shtaros are given from the makneh to the koneh. For example, if I give a field to someone by means of a shtar, I am supposed to give the shtar to the koneh. Shtar erusin is different. There the shtar goes from the koneh, the husband, to the makneh, the wife. Therefore, R' Akiva Eiger explains, the shtar is completely being given to the woman.

In a case where a person frees an eved and the shtar says that some land remains with the adon, so then the very shtar the eved is receiving contains zchuyos of the adon that require the adon's possesion of a shtar. Only then does the Rif say the shtar is bad. This follows the concept in the gemara called "agida gabay". If the shtar is given in such a way that the shtar itself remains somewhat by the adon, that isn't a proper "giving" of a shtar. Essentially, the Rif is saying that lav krus gita is a halachic "agida gabay". However, because the nature of shtarei erusin is that the makneh receives the shtar, there is no agida gabay and no problem with such a shtar.

Rav Chaim in Ishus 3:18 also points out this uniqueness of shtarei erusin. Based on this, he explains that shtaros, in general, are not created by the "daas hamischayev" (i.e. the makneh is usually being mechayev himself by giving away his property). The existence of shtarei erusin prove that the daas of the one who makes the shtar is what creates the shtar. Although, most would assume the daas hamischayev creates shtaros, this is not the case.

In Hilchos Ishus 3:3 the Rambam writes as follows:

ג וְאִם קִדַּשׁ בִּשְׁטָר--כּוֹתֵב עַל הַנְּיָר אוֹ עַל הַחֶרֶס אוֹ עַל הָעַלֶּה וְעַל כָּל דָּבָר שֶׁיִּרְצֶה, הֲרֵי אַתְּ מְקֻדֶּשֶׁת לִי, אוֹ הֲרֵי אַתְּ מְאֹרֶסֶת לִי, וְכָל כַּיּוֹצֶא בִּדְבָרִים אֵלּוּ; וְנוֹתְנוֹ לָהּ, בִּפְנֵי עֵדִים

The Rambam here is paskening that in order to create a shtar erusin one needs to use eidi mesirah - eidim who witness the giving over of the shtar. The question is that in Gerushin 1:16 the Rambam says that by Gittin one may use eidi chasimah b'dieved. Why does the Rambam not say the same thing by shtar eirusin?

Some acharonim answer this question by pointing to the fact that gerushin can be done against the will of the woman. By kiddushin, however, since the daas of the woman is needed, eidi chasimah are no good. The idea is that there must be witnesses present not only to assess the daas of the man, but the woman as well. (See Avi Ezri Ishus 3:3 and Birchas Shmuel Kiddushin Siman 2.)

Others answer using the same yesod that we have been dealing with. The idea is that by gerushin, since the woman is the koneh, so the tefisas hashtar of the koneh can create an anan sahadi as though the eidi chasimah witnessed the giving of the shtar. However, by kiddushin the woman is the makneh. By shtaros we don't say that the tefisas hashtar of the makneh can create such an anan sahadi. Therefore, eidi chasimah are no good by shtar erusin. (See Chazon Ish Even HaEzer 101:11 and Birchas Shmuel Gittin 14.)

The Maharit Alguzi by Get Mekushar in Siman 13 asks a different question on the Rif we started with. He asks from a gemara in Kiddushin 69a where it says that one can free a shifchah and not ubar. Here too, isn't the adon "holding back" the baby for himself? The Shaarei Chaim in Gittin 28 says that this is not a shiyur in the shichrur. The adon is not holding back. Rather, the adon is merely clarifying who he is freeing and who he is not. In such a case it's not a problem of krus gita.

Palginan Diburah

Chaim B. just put up a nice post on Palginan Diburah so I thought it was a good opportunity to write up what I had on the subject.

The Sugyos:

Gittin 8b: A guy writes a shtar to his eved that says "All my property belongs to you". Rava there says that we say palginan diburah. The eved goes free, but gets no property. [The reason he isn't believed on the property has to do with kiyum shtaros. On going free he is believed to say B'fanei Nichtav - like by get isha.]

Gittin 9a: A shchiv m'ra writes over all his property to his eved and then gets healed. On the property the kinyan is chozer, but on the freedom the eved still goes free (because he already has a "shem ben chorin"). This too is a halacha of palginan diburah.

Yevamos 25a/Sanhedrin 9b: Again, the shitah of Rava in two cases. If a guy testifies Ploni ravani lirtzoni or ploni rava ishti l'rtzonah. So on himself or his wife we say he is not believed. For himself he isn't believed because ein adam masim atzmo rasha. On his wife he is a karov. Nevertheless, due to palginan diburah we say he is believed on ploni.

It would seem that Rava in this last sugya is l'shitaso to Gittin where he holds palginan diburah.

Psak Halacha:

The Rambam in Avadim 7:2 and in Eidus 12:2 brings these sugyos l'halacha and seems to pasken palginan diburah.

The Issues:

The Ramban in Makkos 7a asks on Rava's shitah of palginan diburah from the sugya of Ilya v'Tuvia. Ilya and Tuvia were relatives of a guarantor of a loan. The gemara says that this means they are relatives of an involved party and they cannot be witnesses to the loan. The idea is that even though the guarantor is not the actual borrower, since he stands to lose money if the borrower defaults, he too becomes a baal davar. The Ramban asks, what about palginan diburah. Let us say that Ilya and Tuvia are believed as far as the loveh (the borrower) and not as far as the arev (the guarantor).

The Ramban brings the answer of the Raavad. He sets down the following principle. The concept of palginan diburah only applies when the person is testifying about himself. In such a case we say that the eidus is not eidus at all. Thus, we can nullify that part of the testimony and accept the rest. However, by relatives, the eidus on the guarantor is eidus, albeit eidus pasul. If so then we apply a different rule of eidus shebatlah miktsasa batlah kulah. So, according to the Raavad the thrust of the din of palginan diburah is really to say that part of the eidus has no shem eidus. Only then can we say the rest of the eidus is valid, through palginan diburah.


One issue to resolve in the Raavad is the case of Ploni Rava es Ishti. In that case the testimony is about a relative, the guy's wife. For this issue, the concept of Ishto K'gufo is employed so the testimony is, in fact, about the guy himself. Thus, we can still apply palginan dibburah. This is the Raavad's approach to palginan dibburah.


The next step is to address the Rambam's approach to the issue. We will start off by proving that the Rambam does not agree with the Raavad's distinctions. The easiest way to demonstrate this is from eidus 13:13 where the Rambam brings the psul of testifying for one's wife as being a regular psul of karov, like any other relative. Clearly, the Rambam isn't employing ishto k'gufo and thus cannot go with the Raavad's approach.


Also, there is a Raavad found in Mishne Torah Eidus 12:2 that seems l'shitaso, working with the same principle that palginan diburah applies only when someone is testifying about themselves. The Rambam there lists the various cases of palginan diburah and then adds:

וכן כל כיוצא בזה

On this line the Raavad argues that this is not the case. For example, if the case would be ploni rava es shori (my ox), we would not say palginan diburah, but rather eidus shebatlah miktzasa batla kulah. The Ravad is following the same principle that we only say palginan diburah by the baal davar. The implication of the Raavad is that the Rambam makes no such chiluk. In general, the fact that the Rambam never draws this distinction implies he doesn't hold of it. Rav Chaim in eidus 14:4 makes this point in the Rambam.


The Rambam never actually brings the sugya of Ilya and Tuvia l'halacha. The possibility exists that he doesn't bring it for this very reason. The story contradicts the principle of palginan diburah. (See the Grach in Eidus 14:7 discussing these points.)

However, the Rambam does bring some cases that are problematic with the psak of palginan diburah. In Eidus 14:7 the Rambam paskens that if someone writes of shtar giving his property to two people and the eidim are related to one and not the other we say the shtar is no good. The question is why not say palginan and let the eidus work for the party that is not a karov? The Ramban in Makkos actually says that we don't pasken this case l'halacha because we hold palginan dibburah. Obviously, the Rambam has some distinction that we need to discover. Even stranger is that the Yerushalmi (Gittin 1:1) ties this case to the case in Gittin of giving one's property to his eved. This case is based on palginan diburah. So how could the Rambam pasken palginan over there and not here?

These are some of the issues to deal with in palginan diburah. Perhaps in a future post we will address them. Here are some maareh mekomos that deal with the topics we just detailed:

Grach on Rambam 14:7
Ginzei HaGrach 29
Kobetz HeAros Yevamos 21: 1, 12, 13
Grach Stencils 208 (see also Minchas Chinuch Mitzvah 37)
Kobetz Shiurim Gittin 7
Mishnas Rav Aharon Gittin, Biinyan Palginan

Al Hanissim in Al Hamichya Part 3

In a local weekly Torah publication I found the following:

Why is there no mention of Chanukah in Meayn Shalosh? The nature of Meayn Shalosh is that it incorporates the essential parts of benching. The Gemorah regards the Al Hanisim as an askorah, not a part of bentching, therefore it is not included in the Meayn Shalosh.

I already discussed this topic in two previous posts. We brought the Brisker Rav's answer and Rav Soloveitchik's answer. Both were a bit more involved answers than this. I'm not even sure what the answer being given here is, because I don't know to which gemara the writer is referring. The main gemara dealing with the recitation of al hanissim is in Shabbos 24a. I don't see anything there that reflects this answer though. What am I missing?

Selling Chometz Before Pesach

The Ktzos HaChoshen in 194:4 has an interesting discussion about what is the best way to sell chometz before Pesach. He finds a downside to almost every kinyan. For example, kinyan agav may only be d'rabbanan, kinyan chatzer may get into a problem of ein shlichus l'akum, kinyan meshicha isn't practical, kinyan kesef won't really work with m'taltlin etc. The Ktzos then suggests a novel way of transferring the chometz to the non-Jew - by means of a kinyan odisa. What is a kinyan odisa? It comes from a strange story related in the gemara in Baba Basra 149a. Here is a rough translation of that story:

Issur Giyora had twelve thousand zuz by the house of Rava. Rav Mari his son was conceived not in holiness [before his father converted] but born in holiness (thus he did not legally inherit him). (Rashi: This refers to Issur the Ger who had relations with Rochel the daughter of Mar Shmuel before he converted and she became pregnant while he was still a goy with Rav Mari the son of Rochel. Then, while she was pregnant, he converted. Then Rav Mari was born so that his conception was not in holiness but his birth was. [Rochel] was one of the daughters of Shmuel who was held captive as described in Kesuvos 23a.) He was by the house of Rav. Rava said, "How can Rav Mari acquire this money? If by inheritance, he is not an inheritor. If through a matanah, matnas shchiv maira (i.e. the matana of someone prior to his death) is like an inheritance according to the Rabbis. If there is inheritance there can be matnas shchiv maira, otherwise no. If by meshichah, the money is not with him. If by chalipin, money isn't acquired through chalipin. If by kinyan agav, he has no land. If through maamad shlashtan, I'm not going! [Maamad Shlashtan is a kinyan that involves the mafkid, nifkad and the mekabel matana. The mafkid tells the nifkad in the presence of all three, "the money of mine that you have goes to him". Rava didn't want to participate in this, because he would stand to lose the money!] Finally, Rav Ikka the son of Rav Ami asked, "Why not have Issur admit that the money is Rav Mari's and Rav Mari will acquire through kinyan odisa?" After that, an odisa was, in fact, sent out of Issur's house. Rava was upset about this.

The Ktzos understands that Odisa is a real kinyan. If you "admit" that something belongs to someone else, even if, in fact, it doesn't, this can effect a kinyan. By chometz also, the Ktzos suggests writing a contract admitting that the chometz belongs to the non-Jew, and that will create the kinyan.

This idea of a kinyan odisa is relevant to the discussion we had in this previous post about how hodaas baal din works.

It should be noted that not everyone agrees that odisa is a kinyan. Some learn that it is merely an admission. See, for example, the Nimukei Yosef in Baba Basra 69b in Dapei HaRif.

Hodaas Baal Din

It is well known that a person cannot testify about himself l'zchus, for his benefit. However, a person may testify about himself to be mechayev himself. This is the concept of hodaas baal din kmeah eidim. The question is, how precisely does this idea work?

The Ktzos HaChoshen addresses this in a number of places (34:4, 37:1, 5, 9). First, we must address why a person cannot testify about himself l'zchus. The Ktzos brings two possibilities. First, maybe it is merely a chshash mesheker, we fear the person is lying. If so, it is understood why a person would be believed l'chov. The Ir Shushan has a different possibility. He holds that a person isn't believed l'zchus because of the psul of karov. We employ the rule of adam karov eitzel atzmo (a person is related to himself). If this is the case the question remains, why is a person allowed to testify on himself l'chov?

There are many possibilities offered. Some say the person is actually mechayev himself b'toras matanah. It's not that we really believe him that he owes the money. It's just that if he wants to give money to someone else, he is certainly entitled.

Along the same lines, some suggest there is a migo to believe him. After all, he could just give the money as a matanah if he wanted.

The Shach answers that a person isn't a karov to himself l'gabay chov.

Finally, the Ktzos himself learns the whole thing as part of the gezairas hakasuv by modeh b'miktzas, that even though a person is a karov to himself, the gezairas hakasuv overrides.

Al Hanissim in Al HaMichya - The Brisker Rav's Answer

In this previous post we mentioned the question of why it is that we do not mention Chanukah or Purim in the berachah me'ein shalosh. We brought the answer of R' Soloveitchik and I mentioned that I heard there was a Brisker Rav on this as well. Although I still don't know where the Brisker Rav is found, someone called me up and told me the gist of the answer. Here it is:

In regular bentching if someone misses yaaleh v'yavo or retzei and finishes the berachah of bonei yerushalayim there are special berachos that he says as a make-up. The Brisker Rav held that when we mention Shabbos or Yom Tov in the berachah me'ein shalosh, the hazkarah is as a replacement for those berachos, and not as a replacement of the actual yaaleh v'yavo or retzei. One proof to this is that in the beracha me'ein shalosh we place the mentioning of Shabbos and Yom Tov at the end, after Bonei Yerushalayim. If the hazkarah was meant to replace retzei and yaaleh v'yavo, it should go beforehand. Another proof is from the lashon of the hazkarah. When mentioning yom tov in the berachah me'ein shalosh we mention simcha. This is mentioned in the "make-up" berachos, but not in the actual yaaleh v'yavo.

On Chanuka and Purim there are no "make-up" berachos, and therefore no mention of them in the beracha me'ein shalosh.

Why is it that we don't mention actual retzei and yaaleh v'yavo in the berachah me'ein shalosh? To answer this the Brisker Rav pointed to the beracha of havineinu (abridged shemoneh esrai mentioned in the gemara in berachos). In this abridged beracha we do not mention havdalah (if it is motzei shabbos). The idea is that in abridged berachos we don't like to add major hazkaros. For a more detailed reason see Rabbeinu Yonah on this issue of Havinenu. In any case, the Brisker Rav said the same would be with the beracha me'ein shalosh. It too is an abridged berachah like havinenu.

This is basically the answer as I heard it over. Again, I haven't yet seen it inside so I don't want to get too much into the details.

Update Dec. 26, 2007: I finally found the Brisker Rav inside - see here for details.

Nimtza Echad Mehem Karov O' Pasul

There is a halacha in Hilchos Eidus that if even one of the eidim in a set of witnesses is found to be a karov (a relative) or a passul, the entire set of witnesses is thrown out. Based on this halacha there is a famous question dealt with by the rishonim as to how anyone can ever get married. Assuming that at the wedding there is at least one relative who witnesses the maaseh kiddushin, shouldn't we say that nimtza echad mehem karov o' passul eidusan b'tailah. Since one of the witnesses to the marriage is a relative, all the witnesses should be thrown out, and the kiddushin should be nullified.

This issue is addressed by Tosafos in Makkos on daf 6a. Tosafos answers that shaas reiyah alone is not enough to be mitztaref eidim for this halacha. In other words, the halacha of nimtza echad does not kick in at the time the event is witnessed. Rather, if a group of eidim are involved in hagadas eidus (i.e. they are testifying to something in court), only then would the halacha apply.
The Ritva brings a Ramban in Kiddushin with another answer, that the husband can be meyached eidim. If the husband says that these two people are my eidim for the kiddushin and no one else, so everyone else in the crowd is automatically excluded from the eidus, and the kiddushin is valid. Based on this shitah some are noheg in weddings to announce "So and so are eidei kiddushin... to the exclusion of all others".

One question on the Ramban is, what kind of crazy idea is this to be meyached eidim? If someone is about to commit retzicha, can he exclude people who are present from being eidim?

I heard over in the name of R' Soloveitchik that this is one of the reasons to say that when it comes to eidus l'kiyum hadavar, the eidus is actually a part of the maaseh habaal. There are two distinct categories of eidus. One is eidus l'birur hadavar. These are eidim that determine what happened. For example, eidim witness a maaseh retzicha and clarify what precisely took place. Obviously, there is no yichud eidim in this scenario. However, by marriage (and divorce) the eidim are l'kiyum hadavar. They are a part of the maaseh habaal. By being present at the time of the kiddushin they allow the daas of the baal to create the challos kiddushin. They aren't determining what happened, they are actually enabling it to happen. Since eidim l'kiyum hadavar are a part of the maaseh kiddushin, we can imagine a concept of yichud eidim. (For more on this issue of eidus l'kiyum hadavar see Rav Chaim in Yibbum V' Chalitza which we mentioned in this post.)

The Ktzos in Siman 36:6 also addresses this issue of how our weddings work. He gives an answer that is similar to the Ramban's.

Why There is no Al Hanissim in Al Hamichya

Although we mention Shabbos and Rosh Chodesh in the Bracha Me'ein Shalosh (i.e. al hamichya) there is never a mention of Chanukah and Purim. Why not?

I saw in the Iggros HaGrid (Berachos 3:13) that Rav Soloveitchik addresses himself to this question. He explains that when it comes to Shabbos and Rosh Chodesh, the days are mentioned in our tefillos because the days themselves "deserve" mentioning. The inherent kedushas hayom of the day is mechayev hazkarah. Thus, these days are mentioned even in the Bracha Me'ein Shalosh. However, when it comes to Purim and Chanukah, there is no kedushas hayom. The mentioning of al hanissim is not due to the day being mechuyav in hazkarah. Rather, al hanissim is said as an expansion of the bracha of hodaah. Once we thank Hashem in Modim it is fitting to mention the specific miracle of the day. This explains why Chanukah and Purim are not mentioned in the Bracha Me'ein Shalosh. The Bracha Me'ein Shalosh is essentially a "shrinking" of the real Birchas HaMazon. The whole point is to abbreviate, not to expand. Thus, to expand upon Me'ein Shalosh by mentioning the nes of Chanukah or Purim is not appropriate.

I heard that there is also a Brisker Rav that addresses this issue. Does anyone know where it can be found?

Shlichus by Mitzvos

The Ktzos HaChoshen in Siman 182 discusses why it is that shlichus doesn't work by mitzvos. For example, I can't tell my friend to put on tefillin for me as a shliach. Why not? The Ktzos explains that mitzvos are specifically instructed to be b'gufo, I must put the tefillin on my arm. One question on the Ktzos is from the psak of the Rema in Siman 322, that a father cannot appoint a shliach to do the mitzvas milah on his son for him. Why not? Here the mitzvah is not b'gufo?
Rav Chaim (stencils hosafa 5) suggested a different approach. He suggested that shlichus only works on areas of halacha where the mishaleach is a baalim on the dvar hashlichus. As we know, the sources for shlichus come from gittin, kiddushin, and terumah. In all these cases the mishaleach has baalus. For example, if a man appoints a shliach to carry out a kiddushin for him. This is an area of halacha that involves baalus & kinyanim. Because the man is a baalim on his kiddushin, he can appoint a shliach to do the maaseh kiddushin for him.
Evidence to this can be found in the gemara in Kesuvos 74a where it says that only in areas of halacha where one can appoint a shliach, can one make a tnai. The idea according to Rav Chaim is that in both situations, tnai and shlichus, one is demonstrating baalus over the action taking place. (See sefer Eretz HaTzvi by Rav Schachter who brings further proof from Tosafos in that gemara.)
From this logic stems a number of chiddushim regarding a shliach l'kabbalah by a get. We know that by divorce the husband may appoint a shliach to deliver the get on his behalf. This is called a shliach l'holacha. Then, there is another halacha that a woman can appoint a shliach to accept the get on her behalf. This is a shliach l'kabbalah. The Tosafos HaRosh in the beginning of the second perek of Kiddushin asks, why do we need a separate pasuk for shliach l'kabbalah? The answer given is that we know that a woman can be divorced against her will. This is evidence of the fact that a woman cannot exercise any daas when it comes to divorce. If the woman has no daas in this area, it would seem that she lacks baalus, in which case she should not be able to appoint a shliach. This is why a special pasuk is needed to include shliach l'kabbalah. Otherwise such an idea would have been impossible, due to the lack of baalus.
Another famous area of halacha that daas comes up in, is within the issue of eidus l'kiyum hadavar. In normal situations, witnesses are used l'vrurei milsah, to clarify the matter. We use eidim to determine what precisely happened. However, when it comes to gittin and kiddushin, there is another type of eidus, eidus l'kyumei milsah. Witnesses must be present at a marriage and divorce not just to confirm that there was a marriage and divorce, but even to allow the marriage or divorce to take place. Without the eidim, the kiddushin/gerushin cannot even be chal. Rav Chaim in Yibbum V'Chalitza 4:16 points out that by chalitza, eidim are not needed l'kyumei milsah (at least not min hatorah). Why not? He explains that eidim l'kyumei milsah are only needed for davar shebervah that involves daas. Kiddushin and Gerushin involve daas. This is not the case by chalitza. We also find that specifically by shliach l'kabbalah, and not shliach l'holacha, eidim l'kiyum hadavar are needed. It seems that specifically when appointing shliach l'kabbalah, there is "daas davar shebervah" that doesn't exist by shliach l'holacha. This, Rav Chaim discusses in Gerushin 6:9.

Zimun of 10 people

By a zimun of 10 people it is well known that we add "elokenu" to the birchas hazimun. I once heard over in the name of Rav Soloveitchik (maybe from Rav Chaim) that the idea of adding elokenu is to make the zimun into a davar shebikdusha (which of course requires 10 people). The reason why some people stand (by the word elokeinu) is because according to some minhagim, the minhag is to stand during davar shebikdusha (like kaddish or kedusha). This minhag is not universal, however. (For example, I believe some sefardim have the minhag only to stand by a kaddish that leads into another prayer which requires standing.) I also heard that R' Soloveitchik was opposed to people who "half-stand" up by the word elokeinu. Either sit or stand... but half-standing is neither here nor there.
In general, I have heard some interesting shittos from R' Chaim on davar shebikdusha. For example, I heard that Rav Chaim held that davar shebikdusha by definition is responsive davening, chazzan then tzibbur. For this reason he was more in favor of the tzibbur davening in a responsive fashion than all singing together.
I also heard that it was Rav Chaim's minhag to stand even during the kedusha of birchos krias shema (and I think Uva L'tzion as well) due to davar shebikdusha.