How to differentiate between a "revealed" Halacha and Paskened one?

Question

This question mimics a similar question about mathematics - is it discovered or created.

Our Rabbis ruled a lot of Halochos. Some of them are considered "the revelation of the original Halochos G-d gave to Moses", for example, what the Gemmorah (Temurah 16a) says :

במתניתין תנא אלף ושבע מאות קלין וחמורין וגזירות שוות ודקדוקי סופרים נשתכחו בימי אבלו של משה,
אמר רבי אבהו אעפ"כ החזירן עתניאל בן קנז מתוך פלפולו

A different type of Halochos is what the Rabbis ruled by their authority to rule. A good example would be everything that the Rabbis Paskened knowingly against the true Halacha, as in the cases of Tanuro Shel Achnai or that money does not buy in place of Meshicha.

My problem in studying the Talmud is the amount of effort I put into understanding the veracity of a particular ruling: if a Halachah is revealed it should reflect some kind of divine truth, while if it is simply ruled or accepted, it is pretty arbitrary, and there's no way of attesting its veracity.

For example, a Succah's height can't be more than 20 Amas or should be at least 7 Tfochim wide. Is that how G-d sees what a Succah IS, or He didn't care and authorized the Rabbis to come up with whatever their imagination tells them, in a sort of "החדש הזה לכם" - you decide when you want your months to begin.

For all other cases, where it does not say "Halocho Lemoshe MiSinai", is there a way of knowing that what the Rabbis ruled is "Heavenly truth" or a "Rabbinical decree"?

(Needless to say, it has little of a practical difference, as both have the same power.)

Answer 1

Your answer requires more space (and more knowledge) than I have here, but I'll give it a shot, using Rambam's introduction to the Mishnah. (But please read the whole Introduction if you can.)

Some of the statements of Rabbis are explaining laws that were revealed to Moses as part of the Oral Law. Some of them also have sources in verses that could be used to show that the law is true, and some were just accepted as tradition.

As the Rambam writes

דע כי כל מצוה שנתן הקב"ה למשה רבינו ע"ה נתנה לו בפירושה. היה אומר לו המצוה ואחר כך אומר לו פירושה וענינה.וכל מה שהוא כולל ספר התורה. Know that each commandment that the Holy One, blessed be He, gave to Moshe, our teacher – peace be upon him – was given to him with its explanation. He would say to him the commandment and afterward tell him its explanation and content; and [so too with] everything that is included in the Book of the Torah.

Fortunately for us, the Rambam's case used for illustration is Sukkah.

והנה לך משל שהקב"ה אמר למשה בסכות תשבו שבעת ימים (ויקרא כג): And behold for you an example: When the Holy One, blessed be He, said to Moshe, "You shall live in booths seven days" (Leviticus 23:42);

The Rambam then goes on to give the specific example you asked for:

והודיע שהאכילה והשתיה והשינה בה כלו חובה. ושלא יהיה בחללה פחות משבעה טפחים אורך על שבעה טפחים רוחב. ושלא יהיה גובה הסוכה פחות מעשרה טפחים. And He made known that eating and drinking and sleeping in it is all an obligation; and that its space should not be less than seven finger-breadths long on seven finger-breadths wide, and that the height of the booth not be less than ten finger-breadths [sic, should be handsbreadths -N.T.].

The Rabbis also had the ability to add decrees to protect the original biblical law. The Rabbis have the authority to do this from the verses in the Torah telling the Rabbis to guard the Torah. As the Rambam also explains there

והחלק הרביעי הם הגזרות שתקנו הנביאים והחכמים בכל דור ודור כדי לעשותם סייג לתורה. ועליהם צוה הקדוש ברוך הוא לעשותם והוא מה שאמר במאמר כללי (ויקרא יח) ושמרתם את משמרתי ובאה בו הקבלה (יבמות דף כא.) עשו משמרת למשמרתי. והחכמים יקראו אותם גזרות. And the fourth division are the ordinances that the prophets and the sages ordained in each and every generation, in order to make a fence around the Torah. And about them did the Holy One, blessed be He, command to do them, and it is what He said in the general statement (Leviticus 18:30), "And you will guard My guarding" – and the received tradition came [to explain] (Yevamot 21a), "Make a guarding around my guarding." And the sages called them ordinances.

The Sages were also given authority over financial laws, including to remove money from one person and give it to another, which is called Hefker beis din hefker. As the Rambam explains:

וְכֵן יֵשׁ לַדַּיָּן תָּמִיד לְהַפְקִיר מָמוֹן שֶׁיֵּשׁ לוֹ בְּעָלִים וּמְאַבֵּד וְנוֹתֵן כְּפִי מַה שֶּׁיִּרְאֶה לִגְדֹּר פְּרָצוֹת הַדָּת וּלְחַזֵּק הַבֶּדֶק אוֹ לִקְנֹס אַלָּם זֶה וַהֲרֵי הוּא אוֹמֵר בְּעֶזְרָא (עזרא י ח) "וְכל אֲשֶׁר לֹא יָבוֹא לִשְׁלֹשֶׁת הַיָּמִים כַּעֲצַת הַשָּׂרִים וְהַזְּקֵנִים יָחֳרַם כָּל רְכוּשׁוֹ" מִכָּאן שֶׁהֶפְקֵר בֵּית דִּין הֶפְקֵר: Similarly, at all times, a court has the prerogative to declare money belonging to others as ownerless. It may destroy those funds or give them to whomever they see fit to close any breaches in the faith and to strengthen its observance or to penalize a stubborn and difficult person. The Book of Ezra 10:8 states: "Whoever fails to come in three days according to the advice of the officers and the elders will have all of his property confiscated." From this we learn that when a court declares property ownerless, their declaration is effective.

For example

Even if [its value] appreciated in the hand of the robber, the appreciation is to the one who was robbed. And this is [the understanding] of that which is written in the Torah, "and return the theft that he robbed." And the explanation comes - if it is the same as what he robbed, meaning that it has not changed, he must return it as it is, and even if it appreciated much. But the Sages ordained (Bava Kamma 94b), as a result of the Ordinance of the Penitents, that anything that appreciates in the hand of the robber after the forsaking be his. And [so] when he comes to return it, he calculates with the robbed one how much it was worth at the time of the robbery; and the robbed one pays him the money of that which it appreciated, and takes it. And the Sages have the power to do this thing, since they may do according to their will in a monetary matter - and even against the commands of the Torah. As it is well-known that what the court makes ownerless is ownerless (Yevamot 89b, Gittin 36b).

Answer 2

Rambam Sefer Hamitsvot.

The not revealed are dikduke sofrim

אבל הסבה כי כל מה שיוציא אדם ענפים מן השרשים שנאמרו לו למשה בסיני בבאור והם תרי''ג מצות ואפילו היה המוציא משה בעצמו אין ראוי למנותם.

והראיה על זה כלו אמרם בגמרא תמורה (גמרא תמורה דף טז-א) אלף ושבע מאות קלין וחמורין וגזירות שוות ודקדוקי סופרים שנשתכחו בימי אבלו של משה ואעפ''כ החזירן עתניאל בן קנז מפלפולו שנאמר (יהושע טו-טז) ''כל איש אשר יכה את קרית ספר ולכדה'' וגו' (יהושע טו-יז) ''וילכדה עתניאל בן קנז''.

וכשהיו כך הנשכחות כמה היה הכלל שנשכח ממנו זה המספר, כי גם מן השקר שנאמר שנשכח ממנו כל מה שנודע ובלא ספק היו אותם הדינים המוצאים בקל וחומר ובזולתו מהמדות אלפים רבים ואלו כלם היו נודעים בימי משה.

ונאמר עליהם דקדוקי סופרים כי כל מה שלא שמעו בסיני בבאור הנה הוא מדברי סופרים.

הנה כבר התבאר כי תרי''ג מצות שנאמרו לו למשה בסיני לא ימנה בהן כל מה שילמד בשלש עשרה מדות ואפילו בזמנו עליו השלום כל שכן שלא ימנה בהן כל מה שהוציאו באחרית הזמן, אבל אמנם ימנה מה שהיה בפירוש מקובל ממנו והוא שיבארו המעתיקים ויאמרו שזה הדבר אסור לעשותו ואיסורו דאורייתא או יאמרו שהוא גוף תורה הנה נמנה אותו כי הוא נודע בקבלה ולא בהיקש ואמנם זכרו ההיקש בו והביאו הראיה עליו באחת משלש עשרה מדות להראות חכמת הכתוב כמו שבארנו בפירוש המשנה:

Answer 3

One may say that 'mathematical truth' is created - e.g. the concept of numbers and their operations are created by humans and exist in our heads. But they're created in such a way as to help us explain observable phenomena - which we discover.

Perhaps by analogy (lehavdil e"h), halachic truth is also created, in the sense of what the Rabbis accept as the halacha, goes, since "Lo bashamayim hi". But it is created in such a way as to be in line with the Divine will, as the Rabbis perceive it (assuming they're doing it lishma).