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Logic for Law Students: How To Think Like A Lawyer Summary
Logic is the lifeblood of American law.
Professor Kingsfield in The Paper Chase:
“You come in here with a head full of mush and you leave thinking like a lawyer.”
Think like a Lawyer: employ logic to construct arguments.
Syllogism- a label attach to any argument in which a condition is inferred from two
premises.
3 parts of syllogism
Major Premise- states abroad and general truth
Minor Premise- states a specific and usually a more narrowly applicable truth
Conclusion- draws upon the premises and offers a new insight that is known to
be truth based on the premises
Example: All men are mortals
Socrates is a man
Therefore, Socrates is a mortal.
Basic Principle: What is true of the universal is true of the particular.
Note: A clear well-supported syllogism ensures each conclusion is well-supported with
evidence and gives a judge recognizable guidepost to follow.
(Basic steps) Legal issue in a form of syllogism:
1. States issue in a form by stating the general rule of law that opens your case
2. Describe the key facts of the legal problem at hand
3. Draw your conclusion by examining how the major premise about the law
applies to the minor premise
Example:
Major Premise: Cruel and unusual punishment by a state violates the Eight Amendment.
Minor Premise: Executing a minor is cruel and unusual punishment by a State.
Conclusion: Executing a minor is forbidden by the Eighth Amendment.
(Generic Model) Basic Template:
Major: Doing something (violates the law.)
Minor: The Defendant (did something.)
Conclusion: The Defendant (violated the law.)
Note: Each statement in a syllogism must relate to the other two.
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Enthymeme: an argument founded on syllogism although not all parts of the syllogism
are expressed.
Example:
Good girls get stars on their foreheads.
Lisa is a good girl.
Lisa gets a star on her forehead.
*Lisa gets a star on her forehead because she is a good girl.*
Polysyllogism- a series of syllogisms in which the conclusion of one syllogism supplies
a premise of the next syllogism.
All men are mortal.
Socrates is a man.
Therefore, Socrates is mortal.
All mortals can die.
Socrates is mortal.
Therefore, Socrates can die.
People who can die are not gods.
Socrates can die.
Therefore, Socrates is not a god.
Note: Syllogism is a powerful tool because of its rigid inflexibility
Golden Rule: You can only draw a conclusion about the particular after you
demonstrate that it’s part of the universal class.
Letters for syllogism:
“A” and “E” =universal propositions, “A” positive “E” negative
“I” and “O” =particular propositions, “I” positive and “O” negative
Major premise to be valid: “A” or “E.”
Minor premise and Conclusion: “I” or an “O
Deductive Reasoning: General idea to particular (specific) idea
Inductive Reasoning: Multiple particulars to general idea
It is not absolute; it is a logic of probabilities and generalities, not certainties
Fallacy: Use of poor or invalid reasoning for the construction of an argument.
- construct a general rule from an inadequate number of particulars.
Useful to attorneys- current cases are compared to older ones and outcomes of new case
are predicted on basis of the other’s outcomes (precedence).
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Role of analogy in law- Analogical Reasoning in 3steps:
1. Establish similarities between two cases
2. Announce the Rule of Law imbedded in the first case
3. Apply the Rule to the second case
Deductive Reasoning: major to particulars
Inductive Reasoning: particulars to major
Analogy: particulars to particulars
-makes one-to-one comparison that requires no generalizations or reliance on
universal rules
Note: a proper analogy should identify the respects in which the compared cases or
facts, or resemble one another and the respects in which they differ.
Relevancy—whether the compared traits resemble, or differ from, one another in
relevant respects.
Criteria on how to appraise an analogical argument:
1. The acceptability of the analogy will vary proportionally with the numbers of
circumstances that have been analyzed.
2. The acceptability will depend upon the number of positive resemblances and
negative resemblances.
3. The acceptability will be influenced by relevance of the purported analogies.
*If the relevant similarities outweigh the relevant differences, the outcomes of the cases
should be the same.
Logical limits: When there are more to the story
Note:
An argument that is correctly reasoned may be wrong, but an argument that is
incorrectly reasoned can never be right.
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LOGIC FOR LAW STUDENTS: HOW TO THINK LIKE A LAWYER
Ruggero J. Aldisert,*
Stephen Clowney** and Jeremy D. Peterson***
