LEGAL LOGIC

LEGAL LOGICLogic derived from the Greek word logike or logos which means argument, idea, possessed of reason.- Study of the principles of valid demonstration and inferences.Argumentation theory Study of logic as they relate to every day and practical situation.1Logic is the lifeblood of law.In case after case, prosecutors, defense counsel, civil attorneys, and judges call upon the rules of logic to structure their arguments, law professors, for their part, demand that students defend their comments with coherent, identifiable logic.Our modest claim is that a person familiar with the basics of logical thinking is more likely to argue effectively than one who is not.THE ELEMENTS OF REASONINGI. Words - The smallest units of meaningful, natural language are words. II. SENTENCE/STATEMENTIII. ARGUMENTS A group of statements some of which, called the premises, purport to provide support for the truth of a controversial statement called the conclusion.IV. JUDGMENT/REASONINGAct of making statement: in logic, the mental act of making or understanding a positive or negative proposition about somethingIt is generally expressed in declarative statement ANDsometimes in exclamatory sentence.

WORDWords vs. TermWord has a general meaning than term. The later is used to mean special words in particular fields or subjects.The Reference of word ( what the word refers to) - is the range of application of the word or the class of all things that the word applies to.The Meaning of a word is the cognitive significance conveyed by word. It is captured by conveying the class of all the characteristics that are shared by the things that are in the extension of word.

WORD: MEANING AND DEFINITIONTo define a word is to provide another word or group of words that captures what we do or should understand by w0rd.Kinds of Definitions:1. Reportive (lexical) defining the word by explaining how it is used in the language. It reports the ordinary meaning of word.2. Stipulative it is useful when a brand new term was introduced to our vocabulary, and stipulate that from this point on, the word will have special meaning. It is common in the law. The legislature is free to stipulate at will how they understand the term. It is a tool for convenience.3. Prcising to take an ordinary word that has: a) well-established usage, b) BUT a fuzzy range of applicability and specify that in the context the word will be understood to mean precisely what we say it will mean.example: death has different definition if applied to law on euthanasia and abortion.

SENTENCE, LANGUAGE USESNot all kinds of sentences have a truth value. (eg. Question, command, apology, joke etc.)CLAIM or STATEMENTA sentence about which it makes sense to ask whether it is true or false. It has a truth value.It is the stuff of logic, the focus of attention in reasoning.KINDS OF STATEMENTS1. NECESSARY vs. CONTINGENT2. NORMATIVE vs. DESCRIPTIVE3. SINGULAR VS. CATEGORICAL4. SIMPLE vs. COMPOUNDNECESSARY vs. CONTINGENTNECESSARY STATEMENTCONTINGENT STATEMENTWhose truth value depends on language and logic alone.Statements whose truth value depends upon facts about the wordIt does not convey any new informationIt is informativeMust be either always true or always false. A. Tautology a necessary statement that is always true. B. Contradiction a necessary statement that is always false.May be true or may be falseEx. Either Renato Puno is a justice or Renato Puno is not a justice.Ex. Renato Puno is a Supreme Court Justice.NORMATIVE vs. DESCRIPTIVENORMATIVE STATEMENTDESCRIPTIVE STATEMENTIt does not convey any information about how things are but rather prescribes how things ought to be.It describes or tells us truly or falsely about something or the world.Ex. People ought to obey the laws.Ex. Sometimes people disobey the law.SINGULAR vs. CATEGORICALSINGULAR STATEMENTCATEGORICAL STATEMENTStatements which are about a single thing or situation.Statements which are about classes or categories of things or situation. They assert that a particular class is either in part or as a whole related to another class.Ex. 1. The SC rules on the constitutionality of statutes. 2. ERAP has been found guilty of Plunder. 3. The death penalty is cruel and unusual punishment.Ex. 1. All judges are Filipino Citizens. (pattern All S are P) total inclusion 2. No foreign nationals are eligible to serve as president. (No S are P) total exclusion 3. Some decisions of the Supreme Court are controversial. (Some S are P) partial inclusion 4. Some lawyers are not UB graduates. (Some S are not P) partial exclusionSIMPLE vs. COMPOUNDSIMPLE STATEMENTCOMPOUND STATEMENTIt does not contain any other statement as a component.It contains at least one simple statement as a component.Ex. GMAs impeachment proceedings were closely monitored by many people.Ex. GMA is the president and KABAYAN is the vice-president.TRUTH-FUNCTIONAL COMPOUNDSKINDS OF COMPOUNDSI. CONJUNCTIONSThese are formed with the word and 0r one of its cognates (but, although, also, yet, however etc).RULE:For any 2 statements A and B, the conjunction A and B is true when and only when both component statement A, B are true. Otherwise it is false.A and B are placeholders which represent any statement.Ex. Pedro was found guilty in the criminal trial of physical injuries and he was held liable in the civil trial to pay the damages resulted therein.TRUTH-FUNCTIONAL COMPOUNDSII. DISJUNCTIONThese are formed with the word or and one of its cognates (either, unless).RULE:For any 2 statements A and B, the disjunction A or B, is false when and only when both component statements A,B are false. Otherwise it is true.Inclusive Disjunction this or that and perhaps bothExclusive Disjunction this or that but not bothEx. 1. Either Atty. A cross-examined the witness or Atty. B cross-examined the witness. 2. Guilty or not guilty.TRUTH-FUNCTIONAL COMPOUNDIII. CONDITIONALSThese are formed with the form If _____, then _______. where the blanks are filled by simple statements.The 1st blank is called the antecedent and the 2nd blank is called the consequent of a conditional.RULE:For any 2 statements A and B, the conditional If A then B is false when and only when the antecedent is true and the consequent is false. Otherwise it is true.Ex. If Pedro marries again, then he will have a spouse.TRUTH-FUNCTIONAL COMPOUNDIV. BICONDITIONALSThese are also called equivalence, and they are formed with the expression if and only if.RULE:For any 2 statements A and B, the biconditional A if and only if B is true when both A and B have the same truth value.Ex. Pedro is a criminal if and only if he committed a crime.TRUTH-FUNCTIONAL COMPOUNDV. NEGATIONThe truth value of a negative statement depends on the truth value of the affirmative statement. It is formed with the word not, it is not the case that, or it is false that.It is also formed with the expression neither.nor. (negation of a disjunction)RULE:If the statement A is true, then not A is false, and if A is false then its negation not A is true.Ex. Neither X will be arrested nor Y will be arrested.SUMMARY OF TRUTH CONDITIONS FOR COMPOUNDSA BA and B(Conjunction)A or B(Disjunction)If A then B(Conditionals)A if and only if B(Bi-conditionals)A/B then not A/B(Negation)T TTTTTTF TFTTFFT FFTFFF FFFTTRELATIONS OF STATEMENTSA. EQUIVALENCES RULE: Two statements are equivalent if they have exactly the same truth value.PATTERNS:1. If A then B is EQ to If not A then not B2. If A then B is EQ to Not B unless A3. If A then B is EQ to It is not the case that A and not BEx. If Pedro committed the crime then he will go to prison.RELATIONS OF STATEMENTSB. CONTRADICTIONSRULE: Two statements are contradictory if they have exactly opposite truth values.PATTERNS:1. Any statement A and its negation not A.2. All S are P and Some S are not P.3. No S are P and Some S are P.RELATIONS OF STATEMENTSC. CONTRARIESRULE: Two statements are contraries if they cannot be true, yet they may both be false.Example:1. JR is the single murderer of Juan. RJ is the single murderer of Juan.2. A is a better lawyer than B. B is a better lawyer than A.3. All murderers get the death sentence. No murderer gets the death sentence.III. ARGUMENTS A group of statements some of which, called the premises, purport to provide support for the truth of a controversial statement called the conclusion.ARGUMENTS IN LOGICNot every group of statements is an argument. Requirements:Premise/s a claim that is uncontroversial, and which is offered as a supporting reason for the truth of the conclusion.conclusion a claim that is controversial enough to need justification.Pattern: A. Epichreme a complete argumentAll men are mortal. - premise 1 (major premise)Socrates is a man. premise 2 (minor premise)Thus, Socrates is mortal. - conclusion

B. ENTHYMEMESAlso called as incomplete arguments because some premise/s or even the conclusion is missing. The order of statements is not always that the premises appear first and the conclusion last. Ex. Juan should be in prison, since he murdered Maria.The missing premise is Murderers should be in prison.Arguments are sometimes expressed in this way because the speaker believes that the missing part is so obvious that the audience will readily supply it on their own.Conclusion and premise indicatorsConclusion indicators: therefore, hence, thus, so, consequently, it follows that, accordingly, as a result, we may infer that, for this reason, it is entailed that.Premise indicators: since, because, for, as, given that, inasmuch as, follows from, for the reason that, in view of the fact that.These indicators are usually reliable but sometimes these are missing. Outline method for analyzing arguments1. Locate the passages over all conclusion. What is the point the author is trying to make?2. In what way/s is this conclusion supported? The answer to this yields to the premise.For example:We need to build more prisons in order to cope with the continuous increase in crime. In view of the currently overcrowded prison conditions, many criminals are confined in prison for a much lesser time than they should be. But it is common knowledge that the criminals tend to repeat their crimes when they are out of prison.

Example: To qualify as a citizen of a state for purposes of diversity jurisdiction, a party must (1) currently reside in that state and (2) intend to remain there indefinitely. (Major premise; states a rule of law.) Here, the plaintiff does not currently reside in North Carolina. (Minor premise; makes a statement of fact.) Therefore, the plaintiff cannot be a citizen of North Carolina for jurisdictional purposes. (Conclusion; correctly applies the law to the facts.) Kinds of Arguments/ReasoningFirst, all prospective lawyers should make themselves intimately familiar with the fundamentals of deductive reasoning. - is based on the act of proving a conclusion by means of two other propositions.

Second, students should acquaint themselves with the principles of inductive generalization. Inductive generalizations, used correctly, can help students resuscitate causes that seem hopeless. This involves drawing a general conclusion from a number of particular instances. It is based on the concept of probability. The conclusion reached is not considered a truth, rather it is probably true than not.

Third, reasoning by analogy, another form of inductive reasoningis a powerful tool in a lawyers arsenal. It help solve problems not controlled by precedent. It is based on the argument that because the two examples are like in many ways they are also alike in one further specific way.

Kinds of ArgumentsBASIS OF DISTINCTIONDEDUCTIVEINDUCTIVENecessity vs. probabilityIn a good deductive argument, the truth of the premises necessitates the truth of the conclusion. Ex. All men are mortal, and Socrates is a man. Thus, Socrates is mortalIn a good inductive argument, by contrast, the truth of the premises merely makes the conclusion probable.Ex. The sun has risen every morning to this day. Thus, probably, the sun will rise tomorrow.Criteria of Appraisal

Appraising ValidityValid is one that, on the assumption that the premises are true, has a true conclusion that follows with necessity from the premisesSoundness one which is valid, and has actually true premisesAppraising Strength Test/scale of strength that has very weak arguments at the low end and extremely strong argument at the apex depending on the evidential support that the premises provide for the conclusion BASIS OF DISTINCTIONDEDUCTIVE(Validity)INDUCTIVE(Strength)Methods of AppraisalI. Practical test of validity.II. Validity as a matter of form/pattern.III. Showing invalidity by analogical counter- exampleIV. Equivocation and circular arguments

I. Reasoning from authority

II. Causal Reasoning

III. Analogical Reasoning