Friday, March 30, 2007
The Minchas Chinuch suggests that Rashi and Tosfos disagree over the fundemental definition of the mitzvah of tashbisu. According to Rashi, the mitzvah is an issur aseh which is fulfilled so long as one avoids the possibility of owning chameitz. According to Tosfos, tashbisu is a real aseh that is fulfilled only through a kiyum b'yadayim of actually destroying chameitz.
Returning to R' Akiva Eiger's answer, according to Rashi, just like bal yera'eh is not violated by chameitz found during Pesach so long as one has made all ncessary efforts to remove chameitz beforehand, so too the issur aseh of tashbisu cannot be violated. Only according to Tosfos can one argue that if one discoveres chameitz, even though bal yera'eh has not been violated because one has already done bittul, there still exists a mitzvah b'yadayim to destroy the actual chameitz if one is unwilling to declare it hefker.
Perhaps another dimension to this machlokes revolves around the understanding of bittul as hefker. The Rambam in Hil Nedarim (2:14) famously writes that hefker works like a neder that one accepts not to benefit from the mufkar property. If bittul is just a form of hefker, R' Yosef Engel asks, why are we not concerned with the possibility of sha'aila which would revoke the hefker status - in fact, using the principle of ho'il, just the possibility of revoking the neder should render bittul ineffective (the Rambam writes that it is assur to revoke a neder of hekdesh, but many achronim hold that if one ignores the issur and does revoke the neder it can be undone)? According to the Rambam, one is forced to learn that bittul is far more than ordinary hefker - it is tanatamount to an actual destruction of chameitz, a fulfillment of tashbisu, just as Rashi explains.
Thursday, March 29, 2007
R’ Akiva Eiger answers his question on the Ran by contrasting bittul with other forms of kinyanim. The rule of devarim sheb’lev means that mental reservations have no legal impact on an act of a sale – actions speaks louder than words. However, bittul is itself fundamentally is a mental renunciation of ownership – the verbal declaration is just a means of announcing the change of status our decision has effected. The Ran later writes that bittul is actually even weaker than hefker. Since chamietz is assur b’hana’ah it is inherenly ownerless, but the Torah penalizes someone for keeping it in their possesson – bittul simply negates that penalty from setting in, but is not itself what imposes the status of hefker on the chameitz. Devarim sheb’lev cannot undo action – but they perhaps can undo other devarim sheb’lev and render the original bittul invalid.
R’ Akiva Eiger quotes a second answer from his son in law. Even though bittul suffices to remove the issue bal yera’eh and cannot be undone, if one finds chameitz and delays destroying it, one has violated the positive mitzvah of tashbisu, which commands one to destroy chameitz found in his possession.
This implicit assumption of this answer is that tasbisu is not just an issur aseh, a commandment to passively avoid owning chameitz, but rather demands that one actively and immediately destroy chamietz. This issue is a major debate in Rishonim and Achronim, with many consequences. See Minchas Chinuch, and maybe more later…
Wednesday, March 28, 2007
If bittul alone suffices, why did the Chachamim make a takanah that every person must do a bedika? Ran explains that bittul depends on the willingness of the owner of chameitz to declare chameitz ownerless and void. Faced with valuable chameitz or an appetizing piece of chameitz found in the middle of Pesach, who can insure that the owner of that chameitz remains steadfast in his willingness to renounce ownership? Perhaps the owner will regret, and mentally accept ownership of this newly found piece of chameitz, thereby violating bal yera’eh. Therefore, Chazal instituted bedika to try to insure all chameitz is removed and will not be found.
R’ Akiva Eiger asks on the Ran: bittul is not merely a decision the owner of the chameitz comes to, but is a verbal declaration through which the chameitz becomes ownerless. We have a rule in halacha that devarim sheb’lev ainam devarim – lit. words in the heart are meaningless, e.g. if I sold my car but had in the back of my mind that if I can’t find a better one the sale is invalid, unless I formally express that condition as part of the contract, it has no validity. The world of commerce does not recognize intent or thought as having legal standing. If so, asks R’ Akiva Eiger, why according to the Ran are we concerned lest someone might find chameitz in the middle of Pesach, mentally regret his bittul, and come to violate bal yera’eh – the mental regret of bittul is simply devarim sheb’lev, and devarim sheb’lev cannot undo an action! Once one has declared chameitz hefker through bittul, how can mental regret alone reverse the process and make one the owner of that chameitz?
R’ Akiva Eiger gives two fascinating answers – bli neder more to come…
Tuesday, March 27, 2007
Two issues that are consequential to the dispute: 1) whether one must do a bedika after Pesach if one forgot to do one before Pesach – there is no longer a risk of bal yera’eh, but there is still a risk of eating chameitz she-avar alav haPesach; 2) whether one must do a bedika for chameitz noksha, which according to many Rishonim cannot be eaten, but is not subject to bal yera’eh.
The Aruch haShulchan (633:12) writes that although the common practice is to do bedika in a shule or bais medrash, one should not recite a bracha or say bittul afterwards. If the reason for bedika is bal yera'eh, then there should in fact be no obligation of bedika at all as no one person is the formal owner of the shule and its chameitz; although we do bedika because of the reason of Tosfos, the bracha should not be recited m'safeik. Additionally, since only the owner of chameitz has the power to do bittul, the bittul of the gabai or shamash has no effect.
The gemara (4a) raises a question regarding someone who rents an apartment on 14 Nissan - does the obligation of bedika rest on the landlord who possesses the chameitz, or on the tenant who now possesses the dwelling? R’ Elchanan Wasserman points out that the gemara’s question may hinge on the dispute regarding the reason for bedika. If the reason for bedika is to avoid bal yera’eh, then the obligation of bedika should rest upon the owner of the chameitz. However, if the reason for bedika is lest one come to eat chameitz, then the obligation of bedika should rest upon the person using the dwelling, regardless of whether he is the formal owner of the chameitz or not.
What still needs explaining is why Rashi was concerned with the whole issue of bal yera’eh, if, as Tosfos points out, bittul removes the whole problem. Stay tuned…
Friday, March 23, 2007
The question remains, however, why the command to take the Korban Pesach was given on Rosh Chodesh when it could have just as easily been given on the 10th of the month. What purpose did these 10 days serve? “Mishcha u’kchu” meant Bnei Yisrael first had to separate themselves from the idolatry of Egyptian culture, and only then could they properly offer the korban pesach. Even though we are aware of the Talmudic dispute whether the world was created in Tishrei or Nissan, we usually think of these time periods as sharing a common theme. However, if Rosh Chodesh Nissan is really a Rosh haShana, we can appreciate the Shem m’Shmuels’ chiddush that these 10 days between Rosh Chodesh and 10 Nissan correspond to the aseres y’mei tshuvah which culminate in the kabbalas pnei Hashem (like we find on Yom Kippur) in the korban Pesach and the leil haSeder.
Thursday, March 22, 2007
Tuesday, March 20, 2007
The Ramban writes that the pasuk “VaYidaber Moshe es moadai Hashem el Bnei Yisrael” refers to the takanos of learning hilchos Yom Tov on Yom Tov and reading the Torah parsha of the day, citing the last gemara in Mes. Megillah. The Ramban continues that this same idea is conveyed in Onkelus’s explanation, which he quotes - Onkelus writes that Moshe taught the Jewish people the calculations of the calendar that fix the precise day when each holiday will occur. Isn't this Ramban self-contradictory? What do the instructions of how to calculate a calendar have to do with the takanah of learning hilchos Yom Tov? How can these both be called the same interpretation?
Rav Soloveitchik (in Shiurim l'Zecher Aba Mari) explained that both interpretations convey the same fundamental point. “VaYidaber Moshe es moadei Hashem” means that Moshe and every future Bais Din is charged sanctifying Yom Tov as a special day. How does Bais Din do that? One way is by fixing a calendar which demarcates certain days as special holidays. Another way is by dedicating those days to special activities – to studying the Torah laws of those days and reading Torah parshiyos that are special.
Based on this idea, we better understand the role of learning hilchos Yom Tov. There are two separate functions to studying hilchos Yom Tov: firstly, fulfilling the mitzvah of talmud Torah; secondly, fulfilling the mitzvah of “vaYidaber Moshe es moadai Hashem el Bnei Yisrael”, of creating and enhancing kedushas Yom Tov. The obligation to study the halachos 30 days before Yom Tov is purely a function of the mitzvah of talmud Torah, to know the halachos. The obligation to study halacha on Yom Tov itself fulfills that added dimension of “vaYidaber Moshe es moadai Hashem el Bnei Yisrael”.
Monday, March 19, 2007
I'm not sure how many of them read my blog, but to those who do, thank you.
The seifa of the pasuk continues, “…ba’alosa es isha lizboach es zevach hayamim”, meaning Chanah gave the coat when she went up to offer the annual korban with her husband. Although in pshuto shel mikra the word “es” here means “im”, with, I think the Navi deliberately uses “es” and not “im”. The word “es” indicates a transitive verb – not going up, but bringing up, causing others to go up. I would like to suggest that Chanah did not just for make a me’il for her son, but “ba’alosa es isha”, she caused her husband to go up in ruchniyos and Torah as well.
My son got through is bar mitzvah with flying colors, and although there are many people who deserve thank you’s (more to follow), a special thank you goes to my wife, the one who fashioned the me’il katan which made the bar mitzvah boy what he is, and who “ba’alosa es isha” inspires me as well.
Thursday, March 15, 2007
Modern science cannot explain why the laws of physics are exactly balanced for animal life to exist. For example, if the big bang had been one-part-in-a billion more powerful, it would have rushed out too fast for the galaxies to form and for life to begin. If the strong nuclear force were decreased by two percent, atomic nuclei wouldn’t hold together. Hydrogen would be the only atom in the universe. If the gravitational force were decreased, stars (including the sun) would not ignite. These are just three of more than 200 physical parameters within the solar system and universe so exact that they cannot be random. Indeed, the lack of a scientific explanation has allowed these facts to be hijacked as a defense of intelligent design.Of course, Lanza is not satisfied with that answer and instead proposes a theory of “biocentrism” based on quantum mechanics. His argument is that physical reality is created by the mind, and that is why it so perfectly conforms to our expectations. If that’s the best a rational scientist can come up with, I think G-d is getting the best of the skeptics these days.
As we have seen, the world appears to be designed for life not just at the microscopic scale of the atom, but at the level of the universe itself. In cosmology, scientists have discovered that the universe has a long list of traits that make it appear as if everything it contains—from atoms to stars—was tailor-made for us. Many are calling this revelation the Goldilocks principle, because the cosmos is not too this or too that, but just right for life. Others are calling it the anthropic principle, because the universe appears to be human centered. And still others are calling it intelligent design, because they believe it’s no accident that the heavens are so ideally suited for us. By any name, the discovery is causing a huge commotion within the astrophysics community and beyond.
At the moment, the only attempt at an explanation holds that God made the universe.
By coincidence my son is also making a siyum on Mes. Megillah, and IY”H will be speaking about this takanah. Chazal teachesthat it is a mitzvah to study (shoalin v’dorshin) the laws of each Yom Tov thirty days before the chag (Pesachim 6a). The Sha’gas Arye (and others) ask, if there already exists a takanah to study the halachos thirty days before Yom Tov, why is an additional takanah to study the halacha on the day of Y”T itself necessary?
The Ran is medayek in the words shoalin v’dorshin, we ask about the halachos and explain them. Ran writes that this takanah is not an obligation to study halacha, but a direction to poskim and Rabbis as to how to prioritize questions. Within thirty days before a Yom Tov any query that relates to the upcoming holiday takes precedence over other questions and research. The takanah referred to at the end of Mes. Megillah is a separate din that teaches that one should study the laws of Yom Tov on the day of the holiday itself.
The majority of Rishonim (see Biur Halacha, O.C. 429), however, do not learn like the Ran and explain shoalin v’dorshin simply as an obligation to study halachos. According to this reading, the question of overlapping takanos remains. Stay tuned for more...
In addition to the prohibition of building the Mishkan on Shabbos and Yom Tov, the Rambam tells us (Bais haBechira 1:12) that Mishkan can be built only by day and not by night. In the very same halacha the Rambam tells us that both men and women are obligated in the mitzvah of building a Mishkan. The Marcheshes asks: if the Mishkan can only be built during specific time periods, why is it not categorized as a mitzvas aseh she’hazman gerama from which women are exempt? A whole range of answers are possible, some of which my son will hopefully speak about this Shabbos.
Wednesday, March 14, 2007
Maybe it bothers me because my son is also named Eliezer, but whatever the reason, I am baffled. There is a piece in the Piecezna’s sefer Aish Kodesh that explains how Moshe Rabeinu wanted to pass to his children davka the message of Parah Adumah, but this strikes me as missing the main point. The Midrash seems to be highlighting some aspect specifically of the words of Rabbi Eliezer which captivated Moshe Rabeinu. Why was Moshe captivated by Rabbi Eliezer and this halacha in particular more than any other Mishna or meimra in shas???
It seems from R’ Akiva Eiger that the issue here is how to define the role of seviya. Is it the act of eating which triggers the obligation of bentching, and satiation is just a condition (a tnai) in the definition of eating, or is it the state of being satiated itself which obligates bentching, provided that state occurs through an act of eating.
Another possible way to view the safeik here is whether a katan, though he has no chiyuv, can have a kiyum mitzvah. R’ Soloveitchik brought a proof to this issue from the case of a katan who becomes bar mitzvah in between Pesach rishon and Pesach sheni. The Rambam paskens (K.P 5:7) that as long as a katan was counted in a group that brought the first korban pesach, he need not bring a pesach sheni. Even though the katan had no chiyuv to participate in the first korban pesach, he still gains a kiyum mitzvah from doing do which exempts him from pesach sheni (this proof is cited by R’ Reichman in Reshimos Shiuirim, Mes. Sukkah; however, see GR’Ch al haRambam there). Perhaps by birchas hamazon as well, though the katan had no chiyuv to bentch, his birchas hamazon counts as a kiyum mitzvah min haTorah. This safeik is relevant to many other areas as well, including the famous case of a katan who becomes bar mitzvah during sefira.
Tuesday, March 13, 2007
Monday, March 12, 2007
Chazal (Sanhedrin 7) justify Ahron’s choice to fashion the eigel by citing the pasuk promising destruction “Im yehareig b’mikdash Hashem kohein v’navi”, if a kohein and prophet be killed. Chur, the son of Miriam, who was a prophet, had already been killed by the mob as he tried to oppose them. Had Ahron stood in the way and been killed as well, the punishment to the nation would have been far worse. Therefore, Ahron decided to play along and fashion an eigel, doing his best to stall the people and mitigate the damage.
The Maharasha asks: why does the gemara consider Ahron as having the status of kohein? His election as kohein does not occur until later parshiyos. Maharasha answers that Ahron was a bechor, a first born, and before the election of Levi’im the avodah was entrusted to the bechorim.
We can perhaps answer the Maharasha’s question if we assume that Ahron’s election occurred earlier during the episode described in Parshas Shmos referenced above (Margoliyas haYam). Ahron was not just the kohein in-waiting, but actually had the status of kohein from that early moment onward. This would also resolve the question according to the Midrashic sources that say Miriam was the first-born and not Ahron.
As to why the minhag is to celebrate bar mitzvah on Shabbos and not on one’s birthday, well I guess you will just have to show up to hear some of the divrei Torah that may answer that question.
Friday, March 09, 2007
Thursday, March 08, 2007
Of course, I am cheating a bit because I ignored Rashi, which is what prompted Anonymous' comment. Rashi writes (see 21:18) that “ain mukdam u’muchar baTorah”, the Torah parshiyos are not in chronological order. The command to build a Mishkan came only after Yom Kippur, after the completion of the entire process of receiving the Torah and being granted atonement for the cheit haeigeil. According to this view, the parshiyos of Terumah and Tetzaveh, which are read before Ki Tisa, actually chronologically occurred afterwards.
It seems to me that Ramban and Rashi differ on two fundamental issues. Firstly, the Ramban in many places writes that the principle of “ain mukdam u’mecuchar” should not be invoked unless there is a very compelling reason to do so – without strong evidence to the contrary, we assume the Torah does follow a chronological order. The Ibn Ezra, and perhaps Rashi, do not assume a chronological framework – they are much more liberal in applying “ain mukdam” and rearranging timelines. Secondly, this dispute perhaps relates to the function of the Mishkan, as discussed in previous posts. According to the Ramban, the Mishkan was an extension of the experience of Har Sinai, part of the process of kabbalas haTorah. It makes perfect sense that the original command to build a Miskan (P’ Terumah-Tetzaveh) should occur in the context of the initial occurrence of mattan Torah. Rashi, however, focuses on the role of the Mishkan as a means of atonement for the eigel. Therefore, he assumes it could only have been commanded after the sin of the eigel occurred.
But, as Anonymous asked, according to Rashi, why indeed should the Torah chop up the Mishkan parshiyos and place Terumah-Tetzaveh before the eigel and vaYakhel-Pekudei afterwards – even if the Torah's order is not chronological, thematically doesn’t it make sense to group all the Mishkan material together?
The Targum explains the word “anveihu” in the pasuk “zeh K-li v’anveihu” as stemming from the root n-v-h, to dwell. Even as early as the week after escaping Egypt, Bnei Yisrael did not want Hashem to pop into their lives for a miracle and then depart – they wanted the Shechina to dwell with them. The parshiyos in Sefer Shmos are the story of this desire and its fulfillment and tie together thematically. Yetziyat Mitzrayim introduced the bond between G-d and Bnei Yisrael; Yam Suf forged the desire for a permanent Mishkan; Yisro/mattan Torah was a prerequisite; finally, Terumah-Tetzaveh is the culmination of the ideal. The chronological reality of events was that the process was never finished. The sin of the eigel interrupted events, and instead of a Mishkan which was an ideal fulfillment of Redemption, we received a Mishkan which was a kapparah. The break in the Mishkan parshiyos, I think, was necessary to reflect two different roles of the Mishkan: one the one hand, the ideal thematic relationship of Mishkan with the process of Redemption, on the other hand, the reality of events as they transpired, which led to a lesser fulfillment of that aspiration.
Wednesday, March 07, 2007
(P.S. you may want to read the author’s humorous “Unauthorized AutoBiography” to learn more.)
Although he does not mention it, it seems to me that the pilpul of the Chasam Sofer should depend on the machlokes Rambam and Ramban discussed in previous posts. According to the Ramban, since each kli functioned as a hechsher mitzvah for a specific type of avodah, we would have anticipated a phrase like “vaYidaber Ashem el Moshe leimor” introducing it. However, according to the Rambam, the kelim are not hechsheirim, but chalakim of the larger mitzvah of building a Mishkan, and one introductory statement should suffice for all the parts.
Tuesday, March 06, 2007
Be that as it may, the Ramban in his commentary to the Torah writes on “l’kavod ul’tiferes” that the bigdei kehunah had to be made lishma, with the proper kavanah that these garments would be used as bigdei kehunah. The Rambam, as the Minchas Chinuch notes, nowhere cites such a requirement. (The point seems to be a machlokes in the Yerushalmi).
This is pure speculation which may not make sense, but perhaps this machlokes is also l’shitasam. If bigdei kehunah are a hechsher mitzvah to avodah, perhaps they take on the requirement of lishma just like avodah itself. But if it is an independent mitzvah, like the Rambam holds, the requirements need not match.
Is making and wearing bigdei kehunah a mitzvah? The Rambam (aseh #33) counts it as one, but the BH”G disagrees. Ramban explain l’shitaso that the wearing of bigdei kehunah is not itself a mitzvah, but is just a hechsher mitzvah to performing avodah. BH”G only counted doing avodah without bigdei kehunah as an issur. The Megillas Esther defends the Rambam l’shitaso as distinguishing between a hechsher mitzvah and a cheilek of a mitzvah. There are many hechsheiri mitzvah which do count as independent mitzvos, e.g. shechting the korban pesach, preparing the ashes of parah adumah – and, according to the Rambam, bigdei kehunah. What does not count as an independent mitzvah is when something is just a part of the broader mitzvah, a cheilek of the mitzvah, e.g. making kelim for the mikdash. It is easy to impose this distinction on mitzvos after the fact based on what the Rambam did or did not count, but I am unclear as to what exactly defines the difference between the two categories. Why indeed is shechting the korban pesach an independent mitzvah and not just a cheilek of the larger mitzvah of properly offering the korban pesach? What rule does one use to determine hechsher or cheilek?
Monday, March 05, 2007
Friday, March 02, 2007
...Subsequently, I heard that a leading Religious Zionist rabbi in a prominent yeshiva had taken thirty minutes out of his Gemara shiur in order to attack what I had said. I called and asked him, “What did I say that merits this great wrath?” He replied, “I think it is a terrible thing to speak in this way, describing the divine command to destroy Amalek as asking a person to do something which ordinarily is not moral. This poses an ethical problem.”
I said to him, “Wiping out Amalek does not conform to what we would normally expect a person to do. Normally, you should not be killing ‘from child to suckling babe.’ But I’m not saying, God forbid, that it is immoral in our case, where God has specifically commanded the destruction of Amalek—‘A faithful God, without iniquity, righteous and upright is He’ (Devarim 32:4). Although generally such an act would be considered immoral, it assumes a different character when God, from His perception and perspective, commands it. The same holds true of the akeida—it demanded that Avraham do something which normally is immoral. But in the context of the divine command, surely it partakes of the goodness and morality of God. We must admit, though, that there is a conflict in this case between the usual moral norm and the immediate tzav given here.”
I recall in my late adolescence there were certain problems which perturbed me, the way they perturb many others. At the time, I resolved them all in one fell swoop. I had just read Rav Zevin’s book, Ishim Ve-shitot. In his essay on Rav Chayim Soloveitchik, he deals not only with his methodological development, but also with his personality and gemilut chasadim (acts of kindness). He recounted that Reb Chayim used to check every morning if some unfortunate woman had placed an infant waif on his doorstep during the course of the night. (In Brisk, it used to happen at times that a woman would give birth illegitimately and leave her infant in the hands of Reb Chayim.) As I read the stories about Reb Chayim’s extraordinary kindness, I said to myself: Do I approach this level of gemilut chasadim? I don’t even dream of it! In terms of moral sensibility, concern for human beings and sensitivity to human suffering, I am nothing compared to Reb Chayim. Yet despite his moral sensitivity, he managed to live, and live deeply, with the totality of Halakha—including the commands to destroy the Seven Nations, Amalek and all the other things which bother me. How? The answer, I thought, was obvious. It is not that his moral sensitivity was less, but his yirat Shamayim, his emuna, was so much more. The thing to do, then, is not to try to neutralize or de-emphasize the moral element, but rather to deepen and increase the element of yirat Shamayim, of emuna, deveikut and bittachon.
I have subsequently thought of that experience on many occasions. I recall once hearing someone, regarded as a philosopher of sorts, raise moral criticisms of various halakhic practices. When asked about these criticisms, I said, “I know that particular person. He doesn’t look for a foundling on his doorstep every morning.”
So what we need to do, I think, is not to weaken our moral sense or that of our children and students. Rather, we need to deepen and to intensify our commitment, our faith, our sense of obedience, our yirat Shamayim. We need to deepen our sense that God has nothing in this world besides yirat Shamayim, and that our moral conscience needs to develop within its context.
I think what R’ Tzadok is telling us is that Amalek preaches to our own shortcomings. Amalek feeds our sense of despondency and yeiush with the knowledge that as Torah and Hashem are one, as surely as we are human and can never attain that 50th gate of Torah, we can never truly have a relationship with Hashem. On the pasuk “Vayelech Agag ma’adanot” the Ishbitza writes that Agag professed a “givun tov”, an outer daintiness that concealed his inner evil. Amalek tells us that we are all just pretenders wearing a “givun tov”, a mask of goodness, for even people we consider models of righteousness still fall short in G-d’s eyes. If so, why bother to try?
Gadol shimusha yoseir m’limuda means that closeness to G-d does not come only from achievements and ability, but comes from desire as well. And where ability and achievement fall short, desire can more than make up the difference. The battle against Amalek, writes R’ Tzadok, was always carried on by descendents of Rachel – by Shaul, by Mordechai, by Esther, who embodied the tzniyus of Rachel. Leah gave birth to the majority of shevatim in Klal Yisrael, but Rachel had within her the burning desire to be able to fill that role.
On Purim we don masks because, as the Ishbitza writes, a Jew is the opposite of Amalek. Whereas Amalek proclaims that goodness is just a mask over man’s inherent shortcomings, a Jew says that shortcoming is just a mask over the inherent goodness of each of soul.
Thursday, March 01, 2007
R’ Sacks quotes the Rambam in the conclusion of his intro to the Yad that the theme of the megillah emphasizes Hashem’s bringing redemption from danger in response to our prayers. Rav Sacks concludes that, “On Purim, we do not merely celebrate the miracles themselves, but rather, the metamorphosis from disaster to tranquility. The contrast is what is critical.” That being the case, ta’anis Esther, whose fasting marks the potential tragedy Haman planned, is an essential component of the pirsumei nisa of Purim itself.
Perhaps this is the difference between the keriah at night, which the Rav saw as preparatory to the actual mitzvas hayom of Purim, and the kerih during the day, which Tosfos’ holds is the primary reading. During the reading of the night, coming immediately at the close of the ta’anis, we are captivated by the danger of the story, as the tragic plans of Haman unfold before our eyes. This reading stands in contrast to the reading during the day, when we already know how the story will end, and focus our attention more on the happy conclusion to be celebrated through seudah and mishloach manos.
Tosfos proves that the day reading is primary from the fact that Purim seudah is done during the day but not the night before. R’ Soloveitchik (quoted in Moadei haRav) used this as a springboard for another interesting distinction between the two readings. The Rav suggested that other Yamim Tovim have a kedushas hayom from which stems all the associated mitzvos of the day. The kedushas hayom of each Yom Tov begins with sunset the previous night. Purim, however, does not have a kedushas hayom which obligates mitzvos. There are mitzvos hayom - mishloach manos, matanos l’evyonim, kerias hamegillah - which must be done on the day of Purim, to the exclusion of the previous night, but nothing more. The reading at night is not part of the mitzvos hayom of Purim, but is just a preparatory act in anticipation of the day of Purim itself.