📚 KS3 Cambridge Law: Formula & Theorem Quick Reference | KS3 剑桥法律：公式定理速查手册
Law is often described as a system of rules, but it also contains many predictable patterns and relationships that function almost like mathematical formulas. This quick reference handbook translates the most important legal principles from the KS3 Cambridge curriculum into easy-to-remember equations and theorems. From criminal liability to contract formation, these formulas help you structure your revision and analyse legal problems with confidence.
法律常被描述为一个规则体系，但它也包含着许多可预测的模式与关系，其运作方式几乎就像数学公式一样。本速查手册将 KS3 剑桥课程中最重要的法律原则转化为易于记忆的等式与定理。从刑事责任到合同成立，这些公式能帮助你梳理复习内容，从容分析法律问题。
1. The Criminal Equation | 犯罪等式
Every criminal offence can be expressed through a core equation that balances the physical and mental elements of wrongdoing. Without both components present, a conviction cannot stand.
每一项刑事犯罪都可以通过一个核心等式来表达，该等式平衡了不法行为的客观要素与主观要素。若缺少两者中的任何一个，定罪便不成立。
Crime = Actus Reus + Mens Rea − Defence
The Actus Reus is the guilty act — the physical conduct, omission, or state of affairs prohibited by law. The Mens Rea is the guilty mind — the intention, recklessness, or negligence accompanying that act. A successful defence, such as self-defence or duress, effectively negates liability by subtracting from the total.
Actus Reus（犯罪行为）是指法律所禁止的身体行为、不作为或状态。Mens Rea（犯罪意图）是指伴随该行为的意图、轻率或过失。一项成功的抗辩，如自我防卫或被迫行为，实际上是通过扣减来否定责任。
2. The Tort of Negligence Formula | 过失侵权公式
In civil law, the tort of negligence provides compensation for careless harm. Its structure can be reduced to a sequence of essential building blocks that must be proved by the claimant.
在民法中，过失侵权行为为因疏忽造成的损害提供赔偿。其结构可以简化为一系列必须由原告证明的基本构成要件。
Negligence = Duty of Care + Breach + Causation + Damage
A duty of care exists when the neighbour principle from Donoghue v Stevenson applies: you must take reasonable care to avoid acts or omissions that you can reasonably foresee would injure your neighbour. Breach occurs when the defendant falls below the standard of a reasonable person. Causation links the breach to the damage, and the harm must not be too remote.
当Donoghue v Stevenson 案中的邻人原则适用时，即存在注意义务：你必须采取合理注意，避免你可以合理预见会伤害邻人的作为或不作为。违反义务发生在被告的行为未达到合理人标准时。因果关系将违反义务与损害联系起来，且损害不得过于遥远。
3. The Doctrine of Precedent (Stare Decisis) | 遵循先例原则
The English legal system operates on a foundational theorem of binding precedent that ensures consistency and predictability. Lower courts must follow the decisions of higher courts when the material facts are similar.
英国法律体系运行在一个具有约束力的先例基础定理之上，以确保一致性和可预测性。当下级法院面临类似案件事实时，必须遵循上级法院的判决。
Binding Precedent = Material Facts ≈ Ratio Decidendi of Higher Court
The ratio decidendi is the legal reason for the decision — the binding part of the judgment. The obiter dicta are remarks made ‘by the way’, which are persuasive but not binding. The hierarchy of courts determines the direction of the binding force: Supreme Court decisions bind all lower courts, while the Court of Appeal binds itself and courts below.
Ratio decidendi（判决理由）是判决的法律依据，即判决中具有约束力的部分。Obiter dicta（附带意见）是“顺带”发表的评论，具有说服力但不具约束力。法院的等级体系决定了约束力的方向：最高法院的判决约束所有下级法院，上诉法院约束自身及下级法院。
4. Parliamentary Sovereignty Theorem | 议会主权定理
A central constitutional theorem in the United Kingdom is that Parliament is the supreme legal authority. No Parliament can bind its successors, and no court may strike down primary legislation.
英国宪制中的核心定理是，议会是最高的法律权威。任何一届议会都不能约束其后届议会，任何法院都不得推翻一级立法。
Parliamentary Sovereignty = Unlimited Law-Making Power − (Domestic Court Review)
This means that Parliament can make or repeal any law. The courts must apply Acts of Parliament even if they seem unjust. However, with the Human Rights Act 1998, courts can issue a declaration of incompatibility, which somewhat complicates the pure model but does not negate sovereignty itself.
这意味着议会可以制定或废除任何法律。法院必须适用议会立法，即使它们看似不公。然而，根据《1998 年人权法》，法院可以发布不一致宣告，这在一定程度上使得纯粹模型复杂化，但并未否定主权本身。
5. The Contract Formation Formula | 合同成立公式
A legally binding contract arises when specific essential ingredients come together. Without any one of them, a contract may be void, voidable, or unenforceable.
当特定的基本要素齐备时，具有法律约束力的合同便告成立。缺少其中任何一项，合同可能无效、可撤销或不可执行。
Contract = Offer + Acceptance + Consideration + Intention to Create Legal Relations
An offer is a clear statement of willingness to be bound on certain terms. Acceptance must mirror the offer and be communicated. Consideration is something of value exchanged between the parties. Intention to create legal relations is presumed in commercial agreements but not in domestic or social arrangements.
要约是愿意按特定条件受约束的明确表示。承诺必须与要约内容一致并传达给要约人。对价是双方之间交换的某种有价值之物。在商业协议中推定存在设立法律关系的意图，但在家庭或社交安排中则不作此推定。
6. The Human Rights Balance Equation | 人权平衡方程
Under the European Convention on Human Rights, many rights are qualified and can be limited if certain conditions are met. This creates a balancing act expressed as a proportionality test.
根据《欧洲人权公约》，许多权利是附条件的，在满足特定条件时可受到限制。这产生了一种以比例原则检验为表现的平衡行为。
Lawful Limitation = Prescribed by Law + Legitimate Aim + Necessary in a Democratic Society
Articles 8–11, such as the right to respect for private life and freedom of expression, are qualified rights. Any interference by a public authority must be prescribed by law, pursue a legitimate aim (like national security or public safety), and be necessary in a democratic society — meaning that there is a pressing social need and the restriction is proportionate.
第 8 至 11 条所规定的权利，如尊重私生活的权利与表达自由，均为附条件权利。公共当局的任何干预必须由法律明文规定，追求合法目的（如国家安全或公共安全），并且是民主社会所必需的——这意味着存在紧迫的社会需要且限制措施是适度的。
7. The Causation Chain Rule | 因果关系链规则
In both criminal and civil law, liability requires a demonstrable link between the defendant’s act and the result. Causation is often broken down into factual and legal components, and any novus actus interveniens can sever the chain.
在刑法与民法中，归责均要求被告行为与结果之间存在可证明的联系。因果关系通常分解为事实与法律两个组成部分，任何新的介入行为都可能打断因果关系链。
Liability = (But For Test) × (Legal Cause) − (New Intervening Act)
The ‘but for’ test asks: but for the defendant’s conduct, would the harm have occurred? If the answer is no, factual causation is established. Legal causation requires that the defendant’s act was the operating and substantial cause of the harm. A novus actus interveniens, such as an unforeseeable natural event or a third party’s voluntary act, may break the chain.
“若非”检验问道：若非被告的行为，损害是否会发生？若答案是否定的，则事实因果关系成立。法律因果关系要求被告的行为是损害发生的有效且实质性原因。一个新的介入行为，例如不可预见的自然事件或第三方的自愿行为，可能打断因果关系链。
8. Defences as Inverse Operations | 抗辩作为逆运算
In the framework of legal equations, defences can be understood as inverse operations that reduce or entirely cancel liability even when the core offence elements are satisfied.
在法律等式框架中，抗辩可被理解为逆运算，即便核心犯罪构成要件已满足，抗辩仍可减轻或完全抵消责任。
Net Liability = Offence Elements − (Full Defence × 1) − (Partial Defence × 0.5)
A full defence, such as self-defence, insanity, or automatism, results in a complete acquittal. A partial defence, such as diminished responsibility or loss of control, reduces murder to voluntary manslaughter. In tort, contributory negligence operates as a partial defence, reducing the damages proportionately to the claimant’s share of fault.
完全抗辩，如自我防卫、精神错乱或无意识行为，导致完全无罪释放。部分抗辩，如减轻责任或失控，将谋杀罪减轻为自愿过失杀人。在侵权法中，共同过失作为部分抗辩，根据原告的过错比例相应减少损害赔偿。
9. The Separation of Powers Theorem | 权力分立定理
A healthy legal system relies on the separation of powers among the legislature, executive, and judiciary. This constitutional theorem prevents the concentration of power and safeguards individual liberty.
一个健全的法律体系有赖于立法、行政与司法机关之间的权力分立。这项宪制定理能防止权力集中，保障个人自由。
Constitutional Balance = Legislature (Makes Law) + Executive (Implements Law) + Judiciary (Interprets Law)
The legislature (Parliament) makes the law. The executive (Government) implements and enforces the law. The judiciary (courts) interprets and applies the law independently. While the United Kingdom does not have a strict separation like some countries, the principle still underpins the rule of law, ensuring no single body holds unchecked power.
立法机关（议会）制定法律。行政机关（政府）实施和执行法律。司法机关（法院）独立解释和适用法律。尽管英国不像某些国家那样实行严格的分立，但该原则仍是法治的基石，确保没有任何单一体持有不受制约的权力。
10. The Justice Scales Principle | 正义天平原理
Justice itself can be envisioned as a balanced scale where equality, fairness, and access must be constantly weighed. This abstract theorem underpins many procedural rules and legal safeguards.
正义本身可被想象为一架天平，其上必须持续权衡平等、公正与诉诸司法的机会。这一抽象定理是众多程序规则与法律保障的基础。
Justice = Equality Before Law + Fair Hearing + Open Court − (Bias + Inequality of Arms)
Everyone is entitled to equality before the law, meaning that no person is above the law. A fair hearing requires an impartial and independent tribunal, the right to present evidence, and the opportunity to challenge the opposing case. Open court principles promote transparency. Factors like judicial bias or inequality of arms (when one party faces a severe disadvantage) tip the scales away from justice.
每个人都有权享有法律面前人人平等，这意味着无人凌驾于法律之上。公正听审要求裁判机关公正独立，有权出示证据并有机会质疑对方主张。公开审理原则促进透明度。诸如司法偏见或武器不平等（一方当事人处于严重不利地位）等因素会使天平偏离正义。
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