deductive-reasoning

Deductive reasoning

Description

Execute rigorous legal deductive reasoning based on formal logic. Use this skill when the user requests "analyze case logic," "verify legal reasoning," "extract syllogisms," "sort out the relationship between case facts and legal provisions," or "judge the validity of legal argumentation." Provide users with a legal reasoning framework based on formal logic, transforming unstructured legal norms and case facts into a valid, testable, and reproducible chain of deductive argumentation (P-F-C).

Instruction steps

Step 1: Input

Read the case file materials provided by the user (in form, classify them into the following three initial states (if missing, temporarily record as empty):

Major premise (Provision, P): Legal rules, including statutory law (laws, regulations, rules) and case law, social norms, etc.
Minor premise (Fact, f/F):
- Natural minor premise (f): Natural events, acts, states, etc. (the party's oral statement or factual narrative, such as "A asked B to transport goods").
- Legal minor premise (F): Events, acts, states with legal significance (the lawyer's or judge's characterization of natural facts, such as "A and B established a transport contract relationship").
Conclusion (hypothesis) (Conclusion, C): Part or final conclusions reached in the adjudication document (such as guilty/not guilty, breach/no breach). Partial conclusions include intermediate conclusions or conclusion hypotheses yet to be verified, such as the issues in dispute summarized by the judge, or the preliminary inferences of the party or lawyer. Example: [Major premise]: empty [Minor premise - legal facts]: empty [Minor premise - natural facts]: Company A entrusted the transport of a batch of goods to consignee Company B; the legal representative of Company A contacted and entrusted a certain automobile transport company by phone to transport them. The automobile transport company did not enter into a written transport contract with Company A. During transport, due to the driver's negligence, a traffic accident occurred, causing damage to the goods. Company B therefore could not receive the goods on schedule and suffered losses. [Conclusion (hypothesis)] To whom should Company B seek compensation? Company B believes it can claim compensation from the transport company.

Step 2: Reasoning

Strictly execute the following two parts, A and B, andcycle alternately, until all logical loops are closed and no further supplementation is needed:

A. Improve the logical structure of each part

Major premise (P): Sort out the logical structure; if there is no explicit provision, supplement the implied major premise. Distinguish the type:
- Categorical syllogism: Applicable to constitutive elements and conditions of establishment. Form: all acts satisfying feature $X$ have legal consequence $Y$.
- Hypothetical syllogism: Applicable to rules of the form "if ..., then ...".
  - Modus ponens: $X \rightarrow Y$; the facts satisfy $X$, $\therefore Y$. (most common)
  - Modus tollens: $X \rightarrow Y$; $\neg Y$, $\therefore \neg X$. (used for defense and excluding legality)
Minor premise (f/F):
1. Clarify the nature, chronological order, causal and subordinate relationships of the events that occurred.
2. Clarify the legal relationships among the subjects, and examine whether a legal relationship exists between each pair of subjects.
3. Exhaust every type of relationship, and mark missing or ambiguous legal relationships.
Conclusion (C): Sort and filter multiple conclusions, and identify and mark "intermediate conclusions".

B. Link relationships and identify the middle term

Note: The middle term is a term that appears in both premises but does not appear in the conclusion. It is the bridge connecting the syllogism, and is usually the "condition part" of a legal rule.

Subsumption of facts (f-F): Link from the natural minor premise to the legal minor premise, and extract and point out the middle term (such as the intermediate concept from "failed to pay the balance" to "fundamental breach").
Finding the norm (F-P): Link from the legal minor premise to the relevant legal major premise, and extract and point out the middle term that triggers the legal provision.
Deriving the conclusion (P-F-C): Reason from the legal major premise and the legal minor premise to the conclusion, write it in a normatively complete syllogistic form, and verify whether the middle term is correctly derived.

Step 3: Output

Each time this skill is invoked, two parts of content must be output strictly according to the following format:

1. Explainable reasoning chain

Use a clear P-F-C structure diagram or hierarchical list to show how the conclusion is traced back and linked step by step to the corresponding major premise through intermediate conclusions, the legal minor premise, and the natural minor premise. Clearly mark the middle term used at each step.

Example:

Subsumption of facts

Natural facts (f: Raw Facts)	Legal minor premise (F: Legal Facts)	Characterization explanation
f1: There is an arrangement for delivery of goods between A and B	F1: There is a contractual relationship between A and B	An arrangement for delivery of goods usually means a sales or supply contract
f2: A entrusts C by telephone to transport the goods	F2: There is a transport contract relationship between A and C	A telephone entrustment can constitute a valid oral transport contract
f3: During transport, C's driver accidentally opened the truck door, causing the goods to be lost; B failed to receive the goods on time and suffered losses	F21: C, as the carrier, whose driver's negligence caused damage to the goods,	The carrier is liable for the negligence of its staff
f3 (same as above)	Consequence of F11: A's performance to B is impossible.	Breach caused by a third party's reason
f5 (missing) ❗ It is not stated whether a contract or agreement exists between B and C	F3 (missing): Whether a contractual relationship exists between B and C	No contractual relationship is stated; by default, no contract exists.

Finding the norm

Legal minor premise F	Corresponding legal norm P	Triggered middle term (Middle Term)
F1: There is a contractual relationship between A and B	P1: Civil Code 465(2): A contract established in accordance with the law is legally binding only on the parties.	Contracting parties
F21: C, as the carrier, whose driver's negligence caused damage to the goods	P3 (first sentence) Civil Code 593：Breach due to a third party's reason → bear liability to the counterparty.	The party in breach due to a third party's reason
F2: There is a transport contract relationship between A and C	P3 (second sentence) Civil Code Article 593：Disputes between a party and a third party → handled according to law or agreement.	Disputes between a party and a third party
F21 (same as above)	P2: Civil Code Article 832：Carrier causes cargo damage → carrier bears compensation liability.	Carrier causes cargo damage
F3 (missing) ❗: Whether B and C are contract parties	P1: Civil Code Article 465(2)：Same as above	Contract parties

Chain of reasoning C1: B seeks reimbursement from A

C1‑1: A owes a contractual obligation to B P1: All contract parties → bound by the contract F1: A and B are contract parties C1‑1: A owes a contractual obligation to B

C1: B may seek reimbursement from A P3‑1: Breach due to a third party's reason → bear liability to the counterparty F21: C's negligence causes A to breach toward B C1: B may seek reimbursement from A

C2′: B seeks reimbursement from C

P1: All contract parties → bound by the contract F3 (missing): B and C are contract parties C2′: B may seek reimbursement from C

C3: A seeks reimbursement from C

C3‑1: C bears compensation liability to A P2: Carrier causes cargo damage → carrier bears compensation liability F21: C causes cargo damage C3‑1: C bears compensation liability to A

C3: A may seek reimbursement from C P3‑2: Dispute between a party and a third party → handled according to law or agreement F2: There is a transport contract relationship between A and C C3: A may seek reimbursement from C

2. Validity explanation report

Verify the form of reasoning according to the following standards, and output a report:

Validity conclusion: Clearly point out which parts of this chain of reasoning are "valid" and which parts are "invalid".
Fallacy explanation: If invalid, specifically point out what kind of logical fallacy it is. When verifying validity, strictly check the following three common logical fallacies:

Affirming the Consequent: - Incorrect form: $P \rightarrow Q$, $Q$, $\therefore P$.
- Explanation: Treating "the result occurred" as "it must be this cause".
Denying the Antecedent:
- Incorrect form: $P \rightarrow Q$, $\neg P$, $\therefore \neg Q$.
- Explanation: Treating "without this cause" as "the result will not occur".
Fallacy of Four Terms:
- Incorrect form: All $A$ are $B$. All $C$ are $D$. $\therefore$ All $A$ are $D$.
- Explanation: The middle term is not truly connected, or the concept is switched (the middle term must be distributed at least once).