Plug: Check out my Rif Yomi blog.
See part 1 in this series.
We are going to get back to Rashi's position, perhaps in the next post, but first we need to cover Rabbenu Chananel's interpretation of the gemara. The gemara again, with Rashi and Rabbenu Chananel, is pictured below:
Rabbenu Chananel, in interpreting the gemara, seems to also assume three states, but these states would appear to be (at least at first glance, but perhaps even at last glance) different from Rashi's three states.
Rabbenu Chananel's 3 states are:
1) Shalom: Defined as the Beis HaMikdash in a built state. Thus, he assumes that the Shalom stated by Rav Chana bar Bizna, in interpreting the pasuk from Zecharia, means that the Beis HaMikdash is built. This would be the entire length of Bayis Sheni and, presumably, in the future, at the time of Bayis Shlishi. He does not explain why this would be considered specifically "shalom." (As we interpreted Rashi, perhaps correctly, Rashi held that Shalom meant Jewish sovereignty, rather than the Beis Hamikdash being built.)
Nowadays is when there is no Shalom = Beis HaMikdash. Therefore, it is subject to the following two states:
2) Yesh Gzerat HaMalchut / Shmad, where there would be fasting.
3) No Gezeiras HaMalchus (but also no Shalom) is what Rabbenu Chananel says is "kegon ata," like now. Therefore, it is optional to fast, and since if they do not wish to, they do not have an obligation to fast, therefore, messengers do not go out to inform people about the date of Rosh Chodesh.
Nowadays, it would certainly seem to be a case where, according to Rabbenu Chananel, there is no "Shalom" for the Mikdash is not built in its place. (Those who seriously maintain that 770 is the mikdash in its place perhaps should be obligated to now eat on the four fast-days, but that is a snort-worthy proposition.) At the same time, there is no gezeras hamalchus or shmad in our days, so it should not be obligatory to fast, but rather optional.
However, on top of this optionality, there may or may not be other considerations -- e.g. the decision not to fast may be a communal rather than personal decision, or else while back then it was optional, since then it has (unfortunately) assumed the status of minhag, such that it cannot be undone or opted out of. This is to be the subject of later posts, beEzrat HaShem.
For now, though, we still have the idea developed in the previous post that according to Rashi, it is forbidden to fast, such that this should perhaps we should be machmir not to fast, and such that overcome the optionality or minhag within the other opinions.
We have the words of the Divrei Yatziv that Rashi actually maintains the same position as Rabbenu Chananel. Bli neder, I will get to address this in the next post in this series.