Why does the mishna prescribe an indirect measure of whether somebody knew about a court ruling?

Question

The mishna in Horayot 1:2 discusses a case where a court made a ruling that something is permitted and then later rescinded the ruling. Meanwhile, somebody did the thing they initially said is permitted -- is he liable? R' Eliezer says that one who is sitting at home is liable and one who has traveled overseas is not, and Ben Azzai explains that this is because the one who's sitting at home could have heard about the updated ruling while the traveler probably could not.

This explanation makes sense in general, but there are cases where somebody who's at home would nonetheless not hear about the updated ruling (for example, someone who is home sick), and we can imagine cases where somebody who's traveled far away could nonetheless hear about the ruling (for example, from someone else who later joins him in that location). I grant that the usual cases (in this time, not in our connected world) are as Ben Azzai explains, but it makes me wonder: why the indirection?

Instead of evaluating people's liability for transgressions based on assumptions rooted in geography, why did Chazal not make a more direct ruling: one who has heard about the update is liable, and one who has not is not? The practical effect seems to be that one who knowingly violated the court's (amended) ruling must bring an atonement offering, but that's something that the individual decides and does anyway, not something the community can compel, right? The person who knew but cites his overseas trip is still going to be held accountable before the divine court, isn't he? And is the one who didn't know, but was at home, really going to be held liable?

Answer 1

I think that the rule you assumed is written in Mishna 1.1.

זה הכלל: התולה בעצמו, חייב. והתולה בבית דין, פטור. ‏

This is the rule, one who follows his own opinion needs to bring a personal Chatat, one who follows the Bet Din needs not bring a personal Chatat.

The mishna 2 treat cases in which he doesn't know that Chachamim changed the Psak. And gives an examples of doubtful cases according to Rabbi Eliezer. The Bartenura explains, the cases are equivalent to a doubt, the man doesn't say "I don't know if I was aware to the changment of not", there are not classical doubt as in the common Korban Asham Talui.

A man doesn't know that Bet din Changed the psak. But he had the possibily to be informed despite he is not informed. This is an intermediate Halachical status of guilt, he needs to bring an Asham Taluy according to Rabbi Eliezer. One example is when he stays in the town of the court, he would easily be informed.

Note that Rabbi Shimeon holds that this man is still minded that the old psak is still relevant, for Rabbi Shimeon there is no status of doubt. We don't follow his opinion Lahalacha, we follow Rabbi Eliezer and Rabbi Akiva and Ben Azay.

If he is not in the town, all Tanayim hold the same rule. It's not easy for him to reach the information, so if he continues to follow the first psak, he must not to bring a personal Chatat and not an Asham Taluy.

But if he is still in the town and is preparing for his trip, we have two opinions in the set of Tanayim who are against rabbi Shimeon.

For rabbi Akiva, he is so busy that he is not guilty at all if he is not informed. He cannot be informed. For Ben Azay, since he is still in the town, he can be informed and needs to bring an Asham Talui.

But if a man is actually informed there is no question, he needs to bring an individual chatat. The discussion is only for a non informed man, if to be not informed is a kind of guilt. In town there is doubtful guilt, out of the town, there is no guilt, and there are intermediary cases.

We can give an example in our world with some similarities, not exactly the same. The government has changed the speed limit on the road. People cannot claim they don't know. If they don't know, this is their problem. But we can assume that if someone was in an isolated place, he can claim he cannot be informed.