Let the Merciful One write only two of the primary categories and derive the other categories from them. Then the tanna says: It is not possible to derive one category from two other categories, as each category has its own unique characteristics, which prevent the derivation of a new category even from a combination of two categories.

Rava said: And with regard to all of the primary categories in the mishna, when you cast the primary category of Pit among them, all of the rest of them can then be derived through an analogy based on the common factor of two categories. This is the case with all of the categories except for Goring, due to the fact that there is room to refute the analogy to teach the halakha of Goring with the following contention: What is notable about all of the other categories? They are notable in that they are forewarned from their outset. Since it is the typical manner of the animal to trample and eat, and the typical manner of fire to burn, and the typical manner of a pit to serve as an obstacle, the owner is always forewarned with regard to safeguarding against damage and is liable to pay full damages for his failure to prevent the damage even the first time. With regard to Goring, the animal is innocuous for the first three instances of damage and only thereafter is the animal forewarned, rendering its owner liable to pay full damages.

And according to the one who says: On the contrary, Goring is superior in the sense that one’s liability in a case of Goring is more apparent, as the objective of the ox’s action is to cause damage, even Goring can be derived from the common factor of two sources.

The Gemara asks: But if all the categories can be derived from another category and Pit, for the purpose of deriving what halakha did the Merciful One write all the primary categories explicitly? The Gemara answers: It is in order to derive their unique halakhot that apply exclusively to each category.

Goring is written explicitly in order to distinguish between the halakhot of damage caused by an innocuous animal and damage caused by a forewarned animal.

Eating and Trampling are written explicitly in order to exempt from liability those whose animals perform the actions in these categories in a public domain.

Pit is written explicitly in order to exempt one from liability for damage to vessels caused when they fall into a pit. The Gemara adds: And according to the opinion of Rabbi Yehuda, who deems one liable even for damage to vessels caused when they fall into a pit, Pit was written in order to exempt one from liability for the death of a person who was killed by falling into a pit. Rabbi Yehuda concedes that the possessor of the pit is exempt because the person who ultimately fell into the pit was capable of avoiding it.

Man is written explicitly in order to render him liable for four additional types of indemnity, beyond the payment of damages for the diminution in value caused when one injures a person.

Fire is written explicitly in order to exempt one from liability for damage caused to a concealed object, e.g., one hidden by grain, that was consumed by fire. The Gemara asks: And according to Rabbi Yehuda, who deems one liable even for damage done to a concealed object damaged by fire, to add what halakha does the Torah mention the category of Fire explicitly?