From Pure Theory of Law to
Logical Jurisprudence
2002/11/7 Kelsen Conference
Hajime Yoshino
Meiji Gakuin University, Tokyo
Contents
•
•
•
•
•
•
•
1 Introduction
2 What is Logical Jurisprudence (LJ)
３ Theory of Legal Sentence
４ On Theory of Legal Reasoning
５ On Theory of Legal System
６ Demonstration of LES-5 based on LJ
７ Conclusion
1 Introduction
• Hans Kelsen’s final purpose in his “Pure Theory of Law (PL)” is to
establish a scientific of law.
• This enterprise has still (or much more) importance in the present
world. We should receive his torch and hold it further. He might,
however, have some limitations.
• If so, we should overpass (overcome) them and develop a new,
true scientific of law.
• I have attempt to make such a scientific theory of law since 1985.
That is “Logical Jurisprudence (LJ)”.
• In this paper, I would like at first to present what is LJ showing the
primitives of LJ and comparing starting points of LJ with that of PL.
• I would like to then discuss the theses of LJ in terms of theory of
legal norm, legal reasoning and legal system, occasionally
comparing them with those of PL.
• I will demonstrate the availability of LJ to realize real legal
reasoning on the platform of LES-5.
• I conclude this paper suggesting our further discussions.
2. What Is Logical
Jurisprudence (LJ)
• Concept of logical jurisprudence
– Logishe Rechtslehre in German
– A developed form of “legal logic” (Juristische Logik)
– It is not merely an application of logic to law but also a
scientific theory of law to establish the true science of
law.
– Logical Jurisprudence has been developed through
the construction of LES-5, a legal reasoning system in
the field of CISG (the United Nations convention on
contracts for the international sale of goods).
– Naming LJ is done by Hajime Yoshino.
Primitives of LJ
• LJ try to explain the whole legal system using
minimum elements.
• LJ starts form three primitives:
• (1) “sentence,”
– LJ consider that norm as a meaning does not exist.
– LJ starts from sentences.
• (2) “validity” of sentence
– legal validity as legal truth
– “is_valid(sentence1, goal1,time1)”
• (3) “inference rule.”
– Modus Ponens: （（A ⇒Ｂ）＆Ａ） ⇒Ｂ
Comparison of the starting points of
LJ with Pure Theory of Law (PL)
•
•
•
•
•
•
•
• PL
Norm as a Meaning
Legal Norm[1]
Imputation (Zurechnung)
Legal Positivism
First Norm and Second
Norm
Basis of Validity: Issued
on the basis of Upper
Norm
Theory of Hierarchical
Structure of Law
•
•
•
•
•
•
•
• LJ
Sentence as a sign
Law Sentence
Material Implication
Scientific Positivism
Object sentence and
meta sentence
Basis of Validity: Logical
Proof through Legal Meta
Inference
Theory of Legal Meta
Rules
3 Theory of Legal Sentence
• LJ starts from legal sentence
• A legal system is to be analyzed and constructed in
terms of three types of alternative fundamental
concepts:
• 1) (Legal) rule sentence and (Legal) fact sentence
• 2) object sentence and meta sentence
• 3) element sentence and complex sentence
• Existence of an obligation and the validity of the
legal object sentence (Fig.2)
Legal rule and fact sentences
• Legal rule sentences:
– “∀X{a(X) ← b(X)}”.
– legal consequence ←legal requirement
– “∀X{become_effective(offer(X,A),T) ←
reach(offer(X,A),offeree(B,X),T)}”
• Legal fact sentences:
– “b(x1)”.
– reach(offer(o1,anzai),offeree(bernard,o1),4_0
5).
Legal elementary and complex
sentences
• Elementary legal sentence
– the smallest unit of legal sentences.
– “One must drive a car under 100 km /hour on a
highway”
• Complex legal sentence
– A group of legal sentences, which has an unique
name
– “The United Nations Convention on Contracts of the
International Sale of Goods”
– a code, parts or sections or an article of the statute
– The concept of a complex legal sentence enables us
to treat the validity of legal sentence at once.
Legal object and meta
sentences
• A legal object sentence describes an object.
– The object in law is the obligation of a person
– “B must pay A the price of $10000”
• A legal meta sentence describes about a legal
sentence
– It describes the validity of a legal sentence.
– “”B must pay A the price of $10000” is valid”.
– “(1) This Convention applies to contracts of sale of
goods between parties whose places of business are in
different States : (a) when the States are Contracting
States; or … ”
Obligation of persons as ultimate normative
state of affairs
• Law ultimately prescribes the obligation of persons.
• People’s conduct is ultimately regulated by obligations
given by law.
• LJ agrees with Kelsen as far as he says that the
obligation is essential in the legal world.
• However, the problem of the existence of the obligation
might cause of philosophical confusing discussion.
• What is that legal obligations exist ?
• LJ considers: that a legal obligation exist means is that
the legal object sentence, which describe the relevant
obligation, is valid.
Figure 2: The Existence of an Obligation and
the validity of the object legal sentence
t0
t1
There is no obligation.
X is
obligatory
T
t2
Obligation X
turns up
event1
event2
t3
Obligation
X exists.
"Xi is obligatory"
becomes valid
"X is obligatory" "X is obligatory"
is valid.
is valid
Obligation X
is expired
There is no obligation
events
legal object sentence
No legal object sentence
is valid.
"Xi is obligatory"
is terminated
No legal object sentence
is valid.
legal meta sentence
5 On Theory of Legal Reasoning
• Legal Reasoning as development process of
legal sentences
• Legal sentences are developed to specialize or
concretize other legal sentence.
• A legal sentence is set to systematize legal
sentences (or to bring them into logical system)
• Setting of legal sentences is related to logical
proof. They are set to establish logical proof.
Legal Reasoning of Law Application
as a process of development of legal sentences
LAW
Statutes
Purpose of
law
（Abstract law）
Legal interpretation
Creation
（Concretized law）
Reasoning of
legal
justification
Facts described
Reasoning
of legal
creation
Event
Individual law
Legal decision
Creation
Concrete
justice
Legal Reasoning Structure
Statutes
Back and forth
Interpretation (Precedents)
Viewing
Common Knowledge of Legal Concept
Interpretation (for the present case)
Create
Legally confirmed facts
Create
Described facts
Create
Event
Legal decision
Create
Reasoning of legal Creation
Reasoning of legal justification
Legal Principles
Purpose of law
Concrete justice
Legal Reasoning Structure–
Contract is concluded
←Offer becomes effective
& Acceptance becomes effective
Back and
Offer becomes effective
←offer is reached
Indication of intention becomes effective
←It is reached
Create
Indication of intention ←Offer
Indication of intention is reached
Create
←It arrives in mailbox
Create
Offer becomes effective
Offer arrives in mailbox
Event
Create
Contract is concluded
Purpose of law
forth viewing
Reasoning of legal creation
Reasoning of legal justification
Example of Concluding
Contracts
Concrete justice
Logical Structure of Reasoning of
Justification and Creation
• Reasoning of legal justification
– Modus Ponens: （（A →Ｂ）＆Ａ）→Ｂ
• Reasoning of legal creation
– Abduction and
– induction
– falsification： Modus Tollens: （(Ａ→Ｂ）＆～Ｂ）
→～Ａ
6 On Theory of Legal System
• The law require a legal system as a deductive system so that a
judgment is, in legal reasoning, justified from the legal system
together with the relevant facts of a event.
• How legal order is to be systematized as a deductive system, that
has been a target of legal philosophical studies.
• LJ analyze and construct a legal system in terms of above three
primitives including three types of alternative legal sentence.
• LJ succeeded in demonstrating the legal system as a deductive
system on those basis.
• Thereby, the concept of validity of legal sentences and legal meta
inference play a important role.
• The final target of legal reasoning is to prove the validity of object
sentences, to identify what kind of sentences describing obligation
are valid.
• On that way, various legal state of affairs is to be proved as well.
Legal meta inference
• Legal sentence, which is applied to solve a
problem, is to be valid. In other words:
• Only valid legal sentence can be applied
as the premises of the legal inference.
• The inference, which decide whether the
legal sentence applied is valid, is called
legal meta inference.
The validity relationship between
legal sentences
• The validity of a legal object sentence is based on the
description of the validity in the legal meta sentence.
• The validity of this legal meta sentences is prescribed by
other legal meta sentences.
• A legal meta sentence that prescribes the validity of a
legal meta sentence can be called a higher or upper
level legal meta sentence.
• The validity of each legal meta sentence is prescribed by
a higher level of legal meta sentence.
• The highest, final level of legal meta sentence can be
called a “basic” or “fundamental” legal meta sentence.
• The validity of the final, highest legal meta sentence is to
be set as fact[1]
Fundamental Legal meta rule
sentence
•
•
•
•
•
(mrl)
A legal sentence S is valid for a goal G at the time T
←→
S becomes valid for G at time T1 before T &
Not(S is terminated for G after T1 and before T).
• This is a fundamental legal meta rule sentence implicitly
taken for granted all regulations.
• Without this rule, no statutory legal sentence works
when it comes to application.
• This rule is the most fundamental among legal meta
rules enabling us to put a mere collection of legal
sentences into a legal system.
Logical structure of contract law
regulating changes in legal
relations
• Legal rule sentences deciding that legal
sentences are valid.
• Logical structure of contract law deciding
accrual of obligation
• Logical structure of contract law deciding
termination of obligations
Right and Duty
Legal rule sentences prescribing “a
legal sentence becomes valid”
• The accrual of validity of a complex
legal sentence follows the accrual of
validity of elementary legal
sentences which belong to it.
• (r01) become_valid(ES,G,T) <• element_complex_sentence(ES,CS)
become_valid(CS,G,T)
&
Changes of legal Relationships (Fig. 3a)
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object sentence by exercising the right
• (3AA2) "A legal sentence 'X has an obligation to
do Z' becomes valid at time T,
• if a legal sentence 'Y has a right to require X to
do Z' is valid, and Y exercises the right to
require X to do Z at time T.”
• (rCISG46): “The buyer has a right to require the
seller to remedy the lack of conformity by repair”
becomes valid,
• if the goods do not conform with the contract.
Legal rule sentences prescribing “a
legal sentence is terminated”
• The validity of elementary legal
sentence is terminated if the complex
legal sentence is terminated.
Changes of legal Relationships (Fig. 3b’)
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(8)
６ Demonstration of LES-5 based
on Logical Jurisprudence
• Go to demo on off-line.
• http://www.meijigakuin.ac.jp/~yoshino/en/
Case 8f
CASE 8f
1. On April 1, a New York manufacturer of agricultural machines, A (Anzai),
dispatched to the Hamburg branch of a Japanese trading company, B
(Bernard),
a letter containing the following proposal: A will sell B a set of
agricultural machines comprised of a tractor and a rake; the price of the
tractor is $50,000; A will deliver the machinery to B by May 10; B must pay
A the price of the machinery by May 20; the machinery will be transported by
an American fright vessel.
2. The proposal reached B's letter box on April 8.
3. On April 9, B telephoned A and said, "I accept your offer. However, I
want the machinery transported by Japanese container ship."
4. A delivered the agricultural machinery to a Japanese container ship at
the port of New York on May 1.
5. The machinery was delivered to B's Hamburg branch on May 31.
6. B examined the machinery on June 5.
7. B paid A $58,000 on May 20. (The market price of the rake was $8,000).
8. On August 10, the machinery malfunctioned because of a defective
connecting gear.
9. B notified A of the malfunction immediately.
10. On September 1, B demanded that A repair the lack of conformity within
one month.
11. A did not repair the defect by October 1.
12. On October 10, B declared the contract avoided.
13. On December 10, B made restitution of the machine to A.
14. On December 20, A made restitution of the $58,000 price to B, plus
interest, and gave compensation for damages B had suffered.
Queries
•
•
•
•
•
•
•
•
•
•
At each of the points of time indicated below, what is the
legal relation that exists between A and B?
1: April 5th
2: April 15th
3: May 5th
4: August 15th
5: September 15th
6: October 5th
7: November 15th
8: December 15th
9: December 25th
•
•
•
•
CISG
Articles
The following articles of the CISG apply to the case:
Article 15(1) An offer becomes effective when it reaches the
(2) An offer, even if it is irrevocable, may be withdrawn
withdrawal reaches the offeree before or at the same time
offer.Article 16(1) Until a contract is concluded an offer
revoked if the revocation reaches the offeree before
dispatched an acceptance.
Article 18(2) An acceptance of an offer becomes effective
moment the indication of assent reaches the offeror. … .
offeree.
if the
as the
may be
he has
at the
• Article 23
• A contract is concluded at the moment when an acceptance of an offer
becomes effective in accordance with the provisions of this
Convention.
• Article 31
• If the seller is not bound to deliver the goods at any other
particular place, his obligation to deliver consists:
• (a) if the contract of sale involves carriage of the goods - in
handing the goods over to the first carrier for transmission to the
buyer;
CISG Articles
•
•
•
•
•
•
•
•
•
Article 38
(1) The buyer must examine the goods, or cause them to be examined,
within as short a period as is practicable in the circumstances.
Article 39
(1) The buyer loses the right to rely on a lack of conformity of the
goods if he does not give notice to the seller specifying the nature
of the lack of conformity within a reasonable time after he has
discovered it or ought to have discovered it.
Article 45
(1) If the seller fails to perform any of his obligations under the
contract or this Convention, the buyer may:
(a) exercise the rights provided in articles 46 to 52;
(b) claim damages as provided in articles 74 to 77.
(2) The buyer is not deprived of any right he may have to claim
damages by exercising his right to other remedies.
CISG Articles
•
•
Article 46
(1) The buyer may require performance by the seller of his obligations
unless the buyer has resorted to a remedy which is inconsistent with
this requirement.
• (2) If the goods do not conform with the contract, the buyer may
require delivery of substitute goods only if the lack of conformity
constitutes a fundamental breach of contract and a request for
substitute goods is made either in conjunction with notice given under
article 39 or within a reasonable time thereafter.
• (3) If the goods do not conform with the contract, the buyer may
require the seller to remedy the lack of conformity by repair, unless
this is unreasonable having regard to all the circumstances. A request
for repair must be made either in conjunction with notice given under
article 39 or within a reasonable time thereafter.
• Article 49
• (1) The buyer may declare the contract avoided:
•
(a) if the failure by the seller to perform any of his obligations
under the contract or this Convention amounts to a fundamental breach
of contract; or
•
(b) in case of non-delivery, if the seller does not deliver the goods
within the additional period of time fixed by the buyer in accordance
with paragraph (1) of article 47 or declares that he will not deliver
within the period so fixed.
Solutions
•
•
•
•
•
•
•
•
•
1) On April 5th, there is no legal relation between the seller A (Anzai) and
the buyer B (Bernard)
2) On April 15th, A has a duty to deliver the farming machine to B by May
10th and B has a duty to pay the price $50,000 to A by May 20th, while B has
right to require A to deliver the goods to B and A has the right to require B
to pay the price to A by May 10th.
3) On May 5th, B has a duty to pay the price $50000 to A by 20 May, while A
has right to require B to pat the price to A by 10 May.
4) On August 15th, A has a duty to recover the damage, while B has right to
claim A the damage and B has right to require A to repair the machine.
5) On September 15th, A has a duty to recover the damage and a duty to repair
the machine, while B has right to claim A the damage and B has the right to
require A to repair the machine which is restricted to exercise.
6) On October 5th, A has a duty to recover the damage and a duty to repair
the machine, while B has right to claim A the damage, B has right to
require A to repair the machine and B has a right to declare the contract
avoided.
7) On November 15th, A has a duty to recover the damage and a duty to
restitute the price paid by B, and B has a duty to restitute the machine
delivered by A, while B has a right to claim A the damage and a right to
require A to restitute the price, and A has right to require B to restitute
the machine.
8) On December 15th, A has a duty to restitute the price paid by B, while B
has right to require A to restitute the price.
9) On December 25th, there is not legal relation between A and B on the
contract.
Changes of legal Relationships (Fig. 3a)
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e
l
(1)
reaches
f
／
e
８
r
b
e
to
B
m
e
s
v
a
l
４
f
O
f
f
e
r
e
f
f
e
c
t
i
i
s
i
v
e
c
e
p
t
.
b
ptance
４
／
９
m
e
s to
v
a
l
hes
A
e
i
d
u
t
y
t
o
r
ig
h t
t
o
re d
q
e query
liv
e
re
th e
v
ed
r
t
h
g
引
４ ／
1
5
B
m
a
y
d
u
t
y
o
t
r
i
g
h
t
(2)
t
o
re
q
A
a
s
a
渡
rh
e
q
u
i
r
e
t
o
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er
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p
d
u
t
y
t
o
す
A
a
Am
ty
o
d
e
l
i
v
e
r
義
r
e
B
q
u
h
５
i
a
r
s
e
a
d
e
l
i
v
e
r
t
h
e
務
d
u
B
t
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y
t
o
t
h
e
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o
o
d
が
t
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o
a
y
p
1
a
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t
y
h
e
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o
os
d
s
s
over
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あ
p
r
t
i
h
日
c
e
e
t
o
o
the
first
る
p
r
A
i
ま
c
b
e
y
５
／
１
r
Japanese
M
a
b
y
y
で
1
0
.
iner
M
a
に
y
Ship
1 a
0 s
t
h a
.
A
h
query
d
u
t
y
t
o
r
ig
h
t
to
p
d
u
t
y
t
o p
５
／
５
t
h
e
ri c
t
h
e
p
r
(3)
d
e
l
i
v
e
r
h
e
g
o
o
d
s
w
the
h
i
c
h
price
５
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1
0
c
o
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f
o
r
m
s
t
o
t
h
e
oods
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c
o ／
n
t
r
a
c
t
５
3
1
ered
to
amines
６
／
５
goods
B
Changes of legal Relationships (Fig. 3b)
8／10
B may
require A
to repair
the
machine.
９／１
９／15
The additional period
expired.
10／１
10／５
B declared the contract
avoided.
10／10
11／15
A recovered the damge.
B restituted the machine.
12／10
12／15
A restituted the
price paid by B.
12／20
12／25
A has a
duty to
deliver
the goods
which
conforms
to the
contract
repair the machine.
B has a duty to
B asked A to repair the
machine within one month.
A has a duty to recover the damage for B.
８／15
B may claim A the the damage.
The machine is operating
out of order
B noticed to A specifying
the nature of the lack of
conformity
Exercise of claim
to repair.
The right
to claim
to repair
is
restricted.
B may
require A
to repair
the machine
B may
declare
the
contract
avoided.
Exerise of right to declare contract avoided
A has
B may
a duty to
claim A
A may
restitute
to
claim
B has
B
restitute
B to
a duty
the price
the price
to
paid by B restitute
paid by B
the
restitute
machine
A the
delivered
machine.
by A.
query
(4)
query
(5)
query
(6)
duty to reco- right to reqire
to repair
ver the damage
right to claim
damage
require
duty to repair righttotorepair
the machine
( restricted )
duty to reco- right to claim
damage
ver the damage
duty to repair right to require
to repair
the machine
duty to reco- right to claim
damage
ver the damage
right to declain
contract avoided
query
(7)
query
(8)
query
(9)
duty to resti- claim to restitute
B the price
tute the price
claim to restitute duty to restiA the machiner
tute machine
duty to reco- right to claim
damage
ver the damage
claim to restitute
A the machiner
duty to restitute machine
There is no
legal relation
Changes of legal Relationships (Fig. 3b’)
m
c
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ope
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e
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t u
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r
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7
(
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e
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5
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o
t
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a
m
he
t
A
a
m
e
t
u
t
(8)
Changes of legal Relationships (Fig. 3a)
nges
＜
＜
f
e n
Q
A
L
t
u
n
e
s
e
s
g
＞
r
w
a
u
l
y
e
e
r
r
Ａ
・
Ｂ
・
Ａ
４
／
T５
h query
e
r
e
i
s
l
e
g
a
l
r
e
l
(1)
reaches
f
／
e
８
r
b
e
to
B
m
e
s
v
a
l
４
f
O
f
f
e
r
e
f
f
e
c
t
i
i
s
i
v
e
c
e
p
t
.
b
ptance
４
／
９
m
e
s to
v
a
l
hes
A
e
i
d
u
t
y
t
o
r
ig
h t
t
o
re d
q
e query
liv
e
re
th e
v
ed
r
t
h
g
引
４ ／
1
5
B
m
a
y
d
u
t
y
o
t
r
i
g
h
t
(2)
t
o
re
q
A
a
s
a
渡
rh
e
q
u
i
r
e
t
o
p
a
y
th
er
p
t
h
e
p
d
u
t
y
t
o
す
A
a
Am
ty
o
d
e
l
i
v
e
r
義
r
e
B
q
u
h
５
i
a
r
s
e
a
d
e
l
i
v
e
r
t
h
e
務
d
u
B
t
月
y
t
o
t
h
e
g
o
o
d
が
t
p
o
a
y
p
1
a
0
t
y
h
e
g
o
os
d
s
s
over
the
あ
p
r
t
i
h
日
c
e
e
t
o
o
the
first
る
p
r
A
i
ま
c
b
e
y
５
／
１
r
Japanese
M
a
b
y
y
で
1
0
.
iner
M
a
に
y
Ship
1 a
0 s
t
h a
.
A
h
query
d
u
t
y
t
o
r
ig
h
t
to
p
d
u
t
y
t
o p
５
／
５
t
h
e
ri c
t
h
e
p
r
(3)
d
e
l
i
v
e
r
h
e
g
o
o
d
s
w
the
h
i
c
h
price
５
／
1
0
c
o
n
f
o
r
m
s
t
o
t
h
e
oods
is
c
o ／
n
t
r
a
c
t
５
3
1
ered
to
amines
６
／
５
goods
B
7. Realizing a legal reasoning
system on the CISG
• The clarification of logical structure of the contract law is applied
to construct a legal reasoning system on the CISG (LES5).
• The relevant knowledge is written at first in the form of logical
flow chart and the represented in CPF in Knowledge Base.
• The inference system and explanation system is written in logic
programming.
• The system can deduce states of legal relationships at any time
point of cases as results of the application of the CISG to
concrete cases.
• It can explain the reason of the deduction.
• The systematization of law in LES5 might prove the legitimacy
and powerfulness of LJ.
８ Conclusion
7. Conclusion
• LJ starts from three primitives: legal sentences, the
yoshino:
validity and inference rules.
On these •
way LJ
of formalization,
the three
change sorts of legal sentences: rule and
identifies the
of legal relations
is described as
a change
fact sentences,
object
and meta sentences, elementary and
of the validity of legal object sentences
complex sentences and.
that describes obligations.
• On the basis of these conceptions, the basic structure of
legal knowledge has been clarified.
On the formalization, the fundamental legal
By taking
up theunder
CISGwhich
as an example, the structure of
meta rule•sentence
is confirmed
every other legal
meta rules
are thus clarified in terms of LJ.
contract
law is
systematized.
• The study results of knowledge clarification by LJ are put
into computer and a legal reasoning system LES5 has been
Thus I clarified the logical structure of
developed, which could prove the legitimacy and power of
contract law system which can deductively
LJ. of the legal relation
prove the change
along with• the
progresssuggest
of events.
I would
that LJ could develop the science of law
cooperating with artificial intelligence approach to law.
Conclusion
• I clarified the structure of contract law by taking up the
CISG as an example from the view point of Logical
Jurisprudence.
• By using three standards of legal sentences, I explicated
the basic structure of legal knowledge which enables us to
systematize contract law.
• Applying the frame to a cases,I formalized the change of
legal relation as a change of the validity of legal
object sentences that describes obligations.
• On the formalization, I found the fundamental legal meta
rule sentence under which every other legal meta rules are
systematized.
• Thus I clarified the logical structure of contract law
system which can deductively prove the change of the legal
relation along with the progress of events.
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