Legal Reasoning and Logic Malec

LEGAL REASONING AND LOGIC Andrzej Malec The process of legal argumentation: 1. Rules of classical logic 2. Rules of legal reasoning

Five groups of Legal Reasoning: 1. Rules of interpretationinterpretation - are used to reconstruct the meaning of legal expressions; the famous rule clara non sunt interpretanda is of this kind 2. Rules of inferenceinference - are used to infer consequences from legal norms. The rules of reasoning: per  reasoning:  per analogia analogiam m (a simili), a contrario, a fortiori (a maiori ad minus, a mi-nori ad maius) are of this kind. 3. Rules of collisioncollision - are used to solve collisions of legal norms; the rule lex posterior derogat legi priori  is  is of this kind 4. Rules used to determine factual circumstances; circumstances ; the rule in dubio pro reo (in dubio pro libertate) is libertate)  is of this kind, 5. Rules of procedure- the procedure-  the rule that a judge should consider arguments of both parties is of this kind. Legal logic- system of rules of legal reasoning. How can we define the relation between legal logic and formal logic? Chaim Perelman opposes Perelman opposes legal logic to formal logic in two ways: 1. He maintains maintains that legal legal logic is a heuristic logic, whereas whereas formal formal logic is just the the logic of  justification 2. He maintains that legal logic is possible only as “material logic”, “nonformal logic”. This peculiarity of legal logic is connected with the fact that many rules of legal reasoning depend on subjective valuations.

Malec’s Criticism: Agreement - Agree that formal logic is not a heuristic logic. - Submits that formal logic doesn’t does n’t offer rules effective in all cases of legal argumentation - Admit that in some cases rules of formal logic could be effective. Example: Rules of Inductive Logic  – used  – used in legal argumentation as a heuristic method. Malec’s Assumption - Posits that it is reasonable to assume that legal logic is a heuristic logic. Hence, legal logic can be considered as a part of methodology of law: the part which deals with problems such as: which legal norm should we use in legal argumentation and how we use it? Legal logiclogic- helps with finding the solution of legal problem. Formal logiclogic- (which includes both kinds of rules: deductive and inductive) helps with  justification of this solution. solution. Malec’s Criticism: Disagreement - Asserts to disagree that legal logic is necessarily necessaril y non formal. - He agree that many rules of of logic are based on subjective valuations. However, many rules of legal reasoning can be formalized quite easily. Moreover, sometimes it is

possible not only to formalize a single rule but also to build a formal system of rules of legal reasoning.

Rules of legal Reasoning 1. First Order Rules of Collision • lex posterior derogat legi priori (later norms suppress earlier norms) • lex superior derogat legi inferiori (superior norms suppress inferior norms) • lex specialis derogat legi generali (particular norms suppress general norms) -

Whenever the use of first order rules leads us to a contradiction, we employ a second order rule.

2. Second Order Rules of Collision lex superior prior derogat legi inferiori posteriori (earlier superior norms suppress later

•

inferior norms • lex superior generalis derogat legi inferiori speciali (superior general norms suppress inferior particular norms), • lex prior specialis derogat legi posteriori generali (earlier particular norms suppress later general norms). -

 A third order rule of collision would be defined and employed in the case of contradiction between second order rules.

System of Predicate Logic E Sup

Sup

 Axiom

He norm is neither superior or inferior in relation tot eh norm The norm is not an inferior norm in relation to the norm

-Sup (-) ESpec

Spec

The norm is neither general or particular in relation to the norm The norm is

1 2

(x)ESup(x, x),

3

(x)(y)(z){ESup(x, y) & ESup(y, z) ⇒ ESup(x, z)},

4 5

(x)Sup(x, x),

6

(x)(y)(z){Sup(x, y) & Sup(y, z) ⇒ Sup(x, z)},

7

(x)(y){−Sup(x, y) ⇒ Sup(y, x)},

8 9

(x)ESpec(x, x),

10

(x)(y)(z){ESpec (x, y) & ESpec (y, z)

11

(x)Spec(x, x),

(x)(y){ESup(x, y) ⇒ ESup(y, x)},

(x)(y){Sup(x, y) & −ESup(x, y) ⇒ −Sup(y, x)},

(x)(y){ESpec(x, y) ⇒ ESpec(y, x)},

 ESpec(x, z)},

⇒

not a general norm in relation to the norm -Spec (-) Epost

Post

The norm is neither later or earlier in relation to the norm The norm is not an earlier norm in relation to the norm

-Post (-)

12

(x)(y){Spec(x, y) & −ESpec (x, y)

13

(x)(y)(z){Spec (x, y) & Spec(y, z)

14 15 16

(x)(y){−Spec (x, y) (x)(y){EP ost(x, y)

17

(x)(y)(z){EP ost(x, y) & EP ost (y, z)

18 19

(x)P ost(x, x), (x)(y){P ost(x, y) & −EP ost(x, y)

20

(x)(y)(z){P ost(x, y) & P ost(y, z)

21

(x)(y){−P ost(x, y)

⇒

−Spec (y, x)},

 Spec(x, z)},

⇒

 Spec(y, x)},

⇒

(x)EP ost (x, x),

 EP ost (y, x)},

⇒

⇒

 EP ost (x, z)},

⇒

−P ost(y, x)},

 P ost (x, z)},

⇒

 P ost (y, x)}.

⇒

The only rules of the system are the rules of predicate logic and the following rules describing the properties of Der (..., ... ): Sup(x, y) −ESup(x, y)

RULE 1

Der (x, y) ESup(x, y) Spec(x, y) −ESpec(x, y)

RULE 2

Der (x, y) ESup(x, y) ESpec(x, y) P ost(x, y) −EP ost(x, y)

RULE 3

Der (x, y)

Conclusion: The system is a formal system as well as a system of legal logic. So, legal logic is not necessarily non-formal.