Legal reasoning – a continental approach and a common law approach.

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Presentation transcript:

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: 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.

Continental legal reasoning: legal syllogism + legal subsuming

Continental legal reasoning: Legal syllogism:  x ( P(x)  Q(x) ) P (a) ________________ Q(a) Every murderer shall be hanged. John is a murderer. ___________________________ John shall be hanged.

Continental legal reasoning: 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.

Common law legal reasoning: Basic idea: If two cases are similar they shall be treated in a similar way.

Common law legal reasoning: legal analogy + legal distinguishing

Common law legal reasoning: 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).

Common law legal reasoning: 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.

Common law legal reasoning: 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)

Common law legal reasoning: 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…..

Common law legal reasoning: 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 as composed of induction and deduction Analogy: a  b (i.e. K(a) and K(b) ) Q(a) _________________________ Q(b)

Analogy as composed of induction and deduction 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)

Analogy as composed of induction and deduction 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)

Analogy as composed of induction and deduction 4 step K(b)  Q(b) K(b) ____________ Q(b) (modus ponens)

Common law legal reasoning as compared to continental legal reasoning: Common law reasoning: Simpler (no need for general rules). Continental reasoning: More complicated (general rules – necessity of subsuming).

Common law legal reasoning as compared to continental legal reasoning: 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 legal reasoning as compared to continental legal reasoning: Common law reasoning – based on the concept of similarity. Continental reasoning – based on the concepts of general rules and deduction. THE END