Faculty of Business and Law

Law Essentials

Learning Law

Legal Reasoning

One of the primary skills of a law student is the skill of critical thinking. This skill is required to help you solve legal problems.

‘If it does not fit you must acquit” – was the defence in the trial of OJ Simpson

In deciding a case, the Judge will apply 'deductive' and 'inductive' reasoning, as well as 'reasoning by analogy'. Different types of legal reasoning are applied so that a Court can discover or create a legal rule to apply to the facts before the Court.

Applying these types of reasoning to legal judgments means you will look behind the actual words used in a judgment to discover what the law is.

The rules of reasoning are rules of logic but not of pure logic in the strict scientific sense. In law, there is no pure formal logic, as in maths or empirical scientific reasoning, where there is one right answer. In law the rules of logic are applied to try to reach the correct answer.

In law, reasoning by analogy means using similar like circumstance to assist in the resolution of the issue at hand.

For example, if I ask 8 students if they are enjoying reading this website and they all say they are, they think its interesting and relevant, then I may reason by analogy to assume that others are enjoying it to.

Of course, this observation may not be valid. It is possible that the people I talked to were the exception. So I may make further investigations to determine the relative strength and weaknesses in my inference, such as:

  • Number of people I talk to, the more people I talk to, the more likely it is that I will have correct reasoning
  • Instance variety, if I talk to people from different jurisdictions, the more instances of liking the subject I obtain will make for a better analogical argument

Inductive reasoning is reasoning from the particular to the general. This means arriving at a general rule from observing a specific example or a number of particular instances ie. a form of logic

Eg. This lecture theatre has tiered seating (the ‘specific example’) so all lecture theatres have tiered seating (the ‘general rule’)

While inductive reasoning argues from the particular to the general deductive, reasoning is reasoning from the general to the particular. In law, deductive reasoning means reasoning based on a general rule of law to determine the appropriate outcome in a specific case:

  • Judges use deductive reasoning to come to a legal conclusion based on a general rule from a previous case
  • The law's reliance on the doctrine of precedent is an example itself of deductive reasoning.
  • Deductive reasoning says that if something is true of a class of things in general, this truth will apply to all members of that class.

Example: The law says you can be married at the age of 18. Jane is married, so she must be over the age of 18.

The OJ Simpson defence is an example of deductive reasoning: “If it does not fit you must acquit”, that is:

  • The killer wore these leather gloves
  • These gloves do not fit OJ
  • Therefore, OJ is not guilty

This argument conveniently distracts from other possibilities, such as OJ wore the gloves even though they were too tight, the gloves got wet and shrunk, OJ was only trying to make them appear not to fit. For example, when a dispute comes before the Court, the Court's purpose is:

  • to establish what has happened,
  • settle upon the applicable law, and
  • apply the law to the facts to see which party should succeed.
Guide to Legal Reasoning and the Common Law

In this document you'll find a guide to legal reasoning and the common law.

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13th July 2012