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Legal reasoning - PowerPoint PPT Presentation

Legal reasoning. – a continental approach and a common law approach. Aim:. use logical notions to describe a difference between a continental approach to legal reasoning and a common law approach to legal reasoning. Continental legal reasoning:. Basic idea:

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Legal reasoning

– a continental approach and a common law approach

• use logical notions to describe a difference between a continental approach to legal reasoning and a common law approach to legal reasoning

Basic idea:

• Having a general norm coded in a legal text we are constructing an individual norm that shall be applied in a particular case.

• General norm: Every murderer shall be hanged.

• Individual norm: John shall be hanged.

• legal syllogism + legal subsuming

Legal syllogism:

 x ( P(x)  Q(x) )

P (a)

________________

Q(a)

Every murderer shall be hanged.

John is a murderer.

___________________________

John shall be hanged.

Legal subsuming:

K(a)  L(a)  ….  N(a)

____________________

P(a)

John took the knife.

John attacked Bill with the knife.

John caused Bill’s death.

________________________________________

John is a murderer.

Basic idea:

• If two cases are similar they shall be treated in a similar way.

• legal analogy + legal distinguishing

Similarity:

• At least one feature – identical.

• At least one feature – different.

• “abcde” and “abcde” are not similar (they are identical).

• “abcde” and “abcdf” are similar.

• “abcde” and “abcfg” are similar.

• “abcde” and “afghi” are similar.

• “abcde” and “fghij” are not similar (they are different).

Legal analogy:

K(a)  L(a)  ….  N(a)

Q(a)

K(b)  L(b)  ….  N(b)

___________________________

Q(b)

John took the knife. John attacked Bill with the knife. John caused Bill’s death.

John was hanged.

Jim took the knife. Jim attacked Dick with the knife. Jim caused Dick’s death.

_______________________________________________________________

Jim shall be hanged.

Legal distinguishing:

K(a)  L(a)  ….  N(a)

Q(a)

K(b)  L(b)  ….  N(b)

X(a)  Y(a)  ….  Z(a)

 X(b)  Y(b)  ….  Z(b)

___________________________

 Q(a)

YES:

John took the knife. John attacked Bill with the knife. John caused Bill’s death.

John was hanged.

Jim took the knife. Jim attacked Dick with the knife. Jim caused Dick’s death.

BUT…..

John was 25 years old. Bill was an innocent gay.

Jim was 12 years old. Dick was not an innocent gay – he tried to rape Jim.

___________________________________Jim shall not be hanged.

Analogy:

a  b (i.e. K(a) and K(b) )

Q(a)

_________________________

Q(b)

• The same result may be achieved by a composition of induction and deduction

• 1 step:

K(a)  Q(a)

____________

K(a)  Q(a)

(tautology of classical propositional calculus)

• 2 step

K(a)  Q(a)

___________

x ( K(x)  Q(x) )

(non-complete induction)

• 3 step

x ( K(x)  Q(x) )

________________

K(b)  Q(b)

(dictum de omni)

• 4 step

K(b)  Q(b)

K(b)

____________

Q(b)

(modus ponens)

Common law reasoning:

• Simpler (no need for general rules).

Continental reasoning:

• More complicated (general rules – necessity of subsuming).

Common law reasoning:

• Simpler (no need for general rules).

• Non monotonic (additional presumptions may change the outcome).

Continental reasoning:

• More complicated (general rules – necessity of subsuming).

• Monotonic (necessity of so called “functional interpretations of law”, i.e. interpretations that are in contradiction with the wording of the legal text but are supposed to be just)

• Common law reasoning – based on the concept of similarity.

• Continental reasoning – based on the concepts of general rules and deduction.

THE END