Discuss here why you think he is obligated by the divine court but exempt from the human court. What is the "peshat" of this source. Try to think this out well before we go on, because the meaning will change later on.
אמר מר הפורץ גדר בפני בהמת חבירו
ה"ד אילימא בכותל בריא בדיני אדם נמי ניחייב אלא בכותל רעוע
The Gemara clarifies each of the cases listed in the baraita. The Master says: With regard to the case of one who breaches a fence that stood before another’s animal, what are the circumstances? If we say it is speaking of a stable wall that would not have fallen by itself, the one who breached it should also be liable according to human laws, at least for the damage caused to the wall. Rather, here the baraita is speaking of an unstable wall that was about to fall and break in any event, and so his action did not actually cause any loss to the owner.
Think about how the gemara understands this differently from the way you might have understood the source above. What, according to the Talmud, makes one "obligated according to a human court"?
אמר מר הכופף קמתו של חבירו בפני הדליקה
היכי דמי אילימא דמטיא ליה ברוח מצויה בדיני אדם נמי נחייב
אלא דמטיא ברוח שאינה מצויה
Compare the thinking here with the previous section. Again, what principle seems to motivate the stammaitic commentary on the baraita.
(ה) הַמַּדְלִיק אֶת הַגָּדִישׁ, וְהָיוּ בּוֹ כֵלִים וְדָלָקוּ. רַבִּי יְהוּדָה אוֹמֵר, יְשַׁלֵּם מַה שֶּׁבְּתוֹכוֹ. וַחֲכָמִים אוֹמְרִים, אֵינוֹ מְשַׁלֵּם אֶלָּא גָּדִישׁ שֶׁל חִטִּין אוֹ שֶׁל שְׂעֹרִים. הָיָה גְדִי כָפוּת לוֹ וְעֶבֶד סָמוּךְ לוֹ וְנִשְׂרַף עִמּוֹ, חַיָּב. עֶבֶד כָּפוּת לוֹ וּגְדִי סָמוּךְ לוֹ וְנִשְׂרַף עִמּוֹ, פָּטוּר. וּמוֹדִים חֲכָמִים לְרַבִּי יְהוּדָה בְּמַדְלִיק אֶת הַבִּירָה, שֶׁהוּא מְשַׁלֵּם כָּל מַה שֶּׁבְּתוֹכוֹ, שֶׁכֵּן דֶּרֶךְ בְּנֵי אָדָם לְהַנִּיחַ בַּבָּתִּים:
(5) One who set fire to a stack of sheaves and in it there were utensils and these caught fire: Rabbi Yehudah says: He must pay back for what was in it. But the Sages say: He pays only for a stack of wheat or barley. If a kid was fastened to it and a slave stood near by, and they were burnt together, he is liable. If there was a slave fastened to it and a kid stood near by and they were burnt together, he is not liable. And the Sages agree with Rabbi Yehudah that if one set fire to a large building, he must pay back for everything in it; for such is the customary for people to leave [their items] in their houses.
I have added this source in here because it serves as the background for R. Ashi's comment about טמון. Learn the mishnah and try to understand the principle that they are arguing about.
אמר מר השוכר עדי שקר
ה"ד אילימא לנפשיה ממונא בעי שלומי ובדיני אדם נמי ניחייב
אלא לחבריה
והיודע עדות לחבירו ואינו מעיד לו
במאי עסקינן אילימא בבי תרי פשיטא דאורייתא הוא (ויקרא ה, א) אם לא יגיד ונשא עונו
אלא בחד
The baraita teaches: And one who knows testimony in support of another but does not testify on his behalf is exempt from liability according to human laws but liable according to the laws of Heaven. With what circumstances are we dealing? If we say that the case involves two people who could testify, and their evidence would render the other party liable to pay, it is obvious that each of them is liable according to the laws of Heaven; he has committed a transgression by Torah law: “If he does not utter it, then he shall bear his iniquity” (Leviticus 5:1). Therefore, it is unnecessary for the baraita to mention this case.
Rather, the case of the baraita concerns a single witness, whose testimony is not sufficient to render another liable, and to which the transgression of Torah law consequently does not apply. Nevertheless, a litigant can be forced to take an oath based on the testimony of a single witness, and refusal to take this oath would obligate the litigant to pay. Therefore, the witness has caused an indirect loss and is liable according to the laws of Heaven.
ותו ליכא והאיכא (סימן העושה בסם ושליח חבירו נשבר)
העושה מלאכה במי חטאת ובפרת חטאת פטור מדיני אדם וחייב בדיני שמים
The Gemara asks: And is there nothing else, i.e., is there no other case in which one is exempt according to human laws but liable according to the laws of Heaven? But there is such a case. And before citing several cases that are not written in the baraita the Gemara presents a mnemonic device: One who performs; with poison; and an agent; another; is broken. The Gemara returns to the first case: One who performs labor with water of purification, which were meant to be used to purify one rendered ritually impure by a corpse, thereby rendering the water unfit for use, or who performs labor with the red heifer of purification, invalidating the animal for use as an element of the purification ritual, is exempt according to human laws, since the damage he caused is not evident, but liable according to the laws of Heaven, as he caused a financial loss.
The Gemara adds: But there is the following halakha: With regard to one who places poison before another’s animal, and the animal eats it and dies, he is exempt according to human laws, since the animal caused its own death, but liable according to the laws of Heaven.
אין מיהא איכא טובא
והני אצטריכא ליה מהו דתימא בדיני שמים נמי לא ליחייב קמ"ל
הפורץ גדר בפני בהמת חבירו
מהו דתימא כיון דלמסתריה קאי מה עביד בדיני שמים נמי לא ליחייב קמ"ל
Talk out the thought process in these sections. Why is the Gemara analyzing the baraitot in this way? How does this compare with the thinking in the rest of the sugya?
הכופף קמתו של חבירו נמי מהו דתימא? לימא מי הוה ידענא דאתיא רוח שאינה מצויה ובדיני שמים נמי לא ליחייב קמ"ל
ולרב אשי דאמר נמי טמון איתמר מהו דתימא אנא כסויי כסיתיה ניהלך ובדיני שמים נמי לא ליחייב קמ"ל
והשוכר עדי שקר נמי מהו דתימא לימא דברי הרב ודברי התלמיד דברי מי שומעין ובדיני שמים נמי לא ליחייב קמ"ל
והיודע עדות לחבירו ואינו מעיד לו נמי מהו דתימא מי יימר דכי הוה (אתינא) מסהדינא ליה הוה מודה דלמא הוה משתבע לשקרא ובדיני שמים נמי לא ליחייב קמ"ל: