LESSON 1: Introduction to Philosophy & 6.

Do not use power to suppress opinions you think

are pernicious, for if you do, the opinions will
Logic suppress you.
7. Do not fear to be eccentric in opinion, for every
opinion now accepted was once eccentric
Philosophy 8. Find more pleasure in intelligent dissent than in
- Philein (“love of” or “friendship for”) and Sophia (“ passive agreement, for if you value intelligence as
wisdom”); coined by Pythagoras (570-495 BCE) you should, the former implies a deeper
- means “love of wisdom” rather than “love of knowledge” agreement than the latter.
- study of fundamental questions about the nature of 9. Be scrupulously truthful even if the truth is
reality, human existence, knowledge, values and beauty inconvenient, for it is more inconvenient when you
try to conceal it.
Nature of Philosophy 10. Do not feel envious at the happiness of those who
- always behind everything that every man sees and live in a fool’s paradise, for only a fool will think
those he does not see, those he experiences and what is happiness.
those which he does not see.
- a science that studies and investigates all sensible Branches of Philosophy
things in terms of their causes, reasons, principles According to theoretical fields of study
and their effects on human existence, and not by 1.1 Metaphysics- examines the nature of reality, of
mere opinions, beliefs and theories alone. beings, and of existence in general analysis. It is a quest
beyond the physical world of man- life after death, heaven,
FIVE BASIC GROUNDS spirit, angels, and God.
1. It cuts all efforts of man in searching and true 1.2 Ontology - it concerns on knowing the nature of man
knowledge and for love of wisdom. and his existence with respect to place and time
2. It has the force to continuously answer the 1.3 Cosmology – the deeper study of the universe as an
never-ending quest for truth & realities. orderly system, its origin, structure, elements, principles
3. It involves critical evaluation of facts and renders and laws underlying its existence and operations
value judgment 1.4 Teleology – it examines and elucidates the presence
4. It treats with mental activities of reasoning in dealing or absence of the purpose and meaning of the existence of
with the multifaceted affairs of life. the universe
5. It makes and shapes the kind of human life. 1.5 Psychology – it deals with the mind or consciousness
1.6 Epistemology – concerned with the origin, nature and
Purpose of Philosophy validity of knowledge in all its forms
1. It expands the knowledge and understanding of 1.7 Theodicy – it focuses on investigating the nature,
man on everything from what is in the past, being, goodness and justice of God, His relationship to
present, and what maybe in the future. man and the things in the universe, and his divinity
2. It is a powerful tool that equips man to more
flexible in confronting various difficulties Practical Fields
3. It widens one's appreciation of the definiteness to 2.1 Semantics – the meaning and linguistics forms of
infiniteness of things or from generalization to words, their symbolic functions and their influence to
specification. human thoughts and behavior
4. It holds importance in problem-solving, persuasive 2.2. Axiology - it investigates the origin, nature and
powers, creating and inventing something, and meaning of values, what is valuable or not
communicating and writing skills. 2.3 Ethics – it investigates the right and the wrong or
propriety of the behavior of man, the moral good and evil
● While faith and Divine Authority have no place in conduct
philosophical quest of true knowledge, it may 2.4 Aesthetics – it concerns on the study of beauty and
serve as guide in starting the quest. the value of works of art, what is beautiful and what is not
● The goal of philosophy is achieved through 2.5 Logic – the science and art that deals with the
systematized and orderly human reasons and not principles or laws of accurate thinking and systematic and
on any authority, as the latter is only a creation of orderly methods of reasoning.
the former.
● Philosophy has reserved the right to render value
judgments and thus it goes beyond the boundaries LESSON 1.1: Introduction to Logic
of all other arts and sciences.
Etymology
10 Commandments in Philosophy - From the Greek word “logos” which means study,
1. Do not feel absolutely certain of anything. reason or speech.
2. Do not think it worthwhile to produce belief by - First introduced by Greek Philosopher Zeno, using
concealing evidence, for the evidence is sure to the term “ logike” to mean “ discourse of thinking “
come to light. or ‘treatise of thought’
3. Never try to discourage thinking, for you are sure
to succeed. Definition
4. When you meet with opposition, even if it is from - Logic is the study of the mental analysis of facts,
your family, endeavor to overcome it with correct thinking, proper presenting of the terms
argument and not by authority, for a victory and reasoning
dependent upon authority is unreal and illusory. - It deals with the principle of deductive and
5. Have no respect for the authority of others, for inductive arguments aimed at distinguishing valid
there are always contrary authorities to be found. or invalid reasoning.
Logic as an Art and Science - reasoning considered SUBSTANCE of matter with
- It is a science for it involves a systematized and no structure
orderly-arranged truth and principles that governs
the propriety of thinking, and the principles of valid • In reasoning, presentation if statement carries both form
reasoning and argument. and material to make it correct (SUBSTANCE AND FORM)
- As an art, it concerns the expression of beauty of • Correct reasoning exists when conclusion is validly
correct thinking and reasoning. derived from given premises, not necessarily the truth

Nature of Logic FUNCTIONS OF LOGIC

- uses critical analysis because it involves various ● develop a system of using CRITERIA to evaluate
stages of thorough intellectual or mental activities arguments
before arriving at correct thinking and reasoning ● determines conditions of arguments/ premises and
and valid inferences. conclusion
- uses words and signs appearing as terms ● used to PROVE, disprove and seek truth and
- directed towards the formation of a correct and correctness of reasoning
valid reasoning, regardless of whether or not the
reasons are in agreement with facts. IMPORTANCE OF LOGIC
1. Guides man in search for truth
LOGIC 2. Develops & perfects reasoning power and
- VALID reasoning, arguments, inferences and expressions
thinking 3. assures both better intrapersonal and
- uses critical analysis interpersonal relationships
- uses words and signs appearing as terms 4. Improves comprehension in philosophy
- critical thinking and logic comes together 5. develops critical and analytical thinking skills
6. Improvings drawing conclusion
Boolean Standpoint- arguments valid due to its structure 7. Helps increase ability to analyze facts
even if it's no substance 8. improves detection of fallacious and logical
Aristotlelean Standpoint- validity of argument with its reasoning
existence (substance and forms) 9. develops value of true knowledge and wisdom
10. distinguishes assumption from implications

CLASSIFICATION OF LOGIC
1. Deductive Logic Knowledge vs Wisdom
● draws conclusion from universal to specific ● knowledge- information and facts through
principle education
2. Inductive Logic ● wisdom- encompasses a deeper understanding of
● based on techniques of probability knowledge, magnified by its application in our daily
lives like introspection and making thorough and
ARRIVING AT VALID REASONING well-considered decisions in life
1. Formal Logic - True knowledge
- reasoning agrees wuth rules, structure, pattern of
parts
- ARGUMENTATION (major premise, minor LESSON 2: Concepts, Terms, Definitions, & Proposition
premise, conclusion
2. Informal Logic (Material Logic) Concepts
- anything that exists in the mind of every person
through sensual perceptions of anything.
-
Development of a Concept
- Empiricists argue that the mind of a newborn
child is a blank slate or tabula rasa
- Behaviors are associated largely to biological
factors and environmental events.
- Individual differences in personality are the
resulting effects of the environmental factors.

● Swiss psychologist Jean Piaget proposed the

cognitive development of mind and the origin
of human knowledge
SIMPLE CONCEPTS >>>>ABSTRACT
SYMBOLS>>HYPOTHESIS>>>>CONCEPT

CLASSIFICATION OF CONCEPTS
As To Sense Receptive
1. Concrete
- something than can be quantified to certain
extent and which quality can be distinguished
from another as a subject
Ex. Man, Animals, Color, Distance
As to Content Quality Phantasm
2. Collective ● A mental process of creating a picture of the
- concerns the mass or content of the subject or percept that contains its description within the
anything as recorded in the mind limits .
- e.g. PEOPLE, AUDIENCE, TEAM, PANEL, ● differ depending on how many times it comes
HERD, AMMUNITION, JEWELRY, MANY, to senses, given the different conditions in
GROUP, CONSTELLATION time.
● One object may be described differently when
1. Divisive placed in two or more different environmental
- stands for a single unit of a thing in the mind conditions, such as in experimental studies.
- e.g. This, he, only, is, cat, cow, me ● Two or more similar objects may have similar
characteristics under similar conditions but
As To Referent may differ as to the number of time it comes to
1. Singular human senses.
- it extends only to a single or group of specific
thing or matter in the mind TERMS
2. Particular - external signs of the mental apprehension
- it has no definite or determinate extension of - made up of signs or symbols as intellectual
meaning in the mind expression
- e.g. Some, many, few, most - external and perceivable sign which connote
3. Universal or denote an idea
- it provides many extensions of meaning in the - have the essential elements of being
human mind as a generic or holistic perceivable, culture-based, time-bounded and
description of everything sign
- e.g. Mankind, plants, animals, all ladies,
Logicians Classification of Terms
● Simple Term
● As to Sign - composed of single word to represent an idea
1. Affirmative or object
- it indicates the existence of anything and - e.g. plier, scissor, plant, school, man, dog
stands for positive confirmation or agreement
- e.g. There is, in favor, yes, true, agree, ● Compound Term
consent. - contains 2 or more words but represent only a
2. Negative single idea or object
- it denies or rejects the existence of a thing or - e.g. ladies drink, colored light, dirty old rich
subject man, sexy dancing queen
- e.g. False, NO, oppose, disagree, dissent
● As to Meaning
● As to Measurability Univocal Term
1. Finite - different spellings & sounds but convey similar
- It stands in the mind as a thing or matter that meaning
is measurable in single units - e.g. teacher & instructor, rock & stone, lawyer
- e.g. Animals, Fruits, Houses & attorney
Equivocal Term
2. Infinite - Same spelling & sound but different meanings
- It stands in the mind as things or matters that - e.g. plant (iceplants & green leafy vegetables)
cannot be measured to a certain limit Analogous
- e.g. Sand, Stars in the Galaxy, Raindrops - same spellings, sounds & essence but are
nominal or symbolic character
Properties of a Concept - E.g. “blind man” & “blind curve”
The expression of a concept depends on the
two properties ● As to Quality or Polarity
○ Affirmative Term
1. Comprehension ○ Negative Term
-the ability of the mind to understand the meaning or
features of the thing in its general perspective and not Definition
just one aspect of it. ELEMENTS OF A DEFINITION
e.g Man as a totality as a higher form of animal 2. Definiens- word or phrase that explains or
describes the defining property of the definiendum.
2. Extension 2 PARTS:
-refers to the objects or things containing all the given A. Proximate genus- is the nearest general class to
features or characteristics. which a thing belongs
The many descriptions given tend to extend the mind B. Specific differentia- essential characteristics that
into more specific or the inferior thing or object differentiates a thing from the rest of the group. (same
described. example)
e.g. Riddles
Example: OTHER TYPES OF DEFINITIONS- When the real
“A bird is an animal with feathers, such as chicken, definition is difficult or impossible to formulate.
owl, and ostrich,”
(animal= proximate genus; feathers = specific 1. Definition by property- gives the attributes
differentia) of a thing instead of its true specific difference.
-Man may be defined on the basis of property or
3. Denotata- provides concrete examples of the attributes as “an animal capable of speech” or “an
extension of the definiendum. (same ex..) animal with religious sentiments.”
Example:
“A bird is an animal with feathers, such as chicken, 2. Definition by logical accident- gives an
owl, and ostrich,” attribute of a thing which may or may not be present in
(chicken, owl, and ostrich are the denotata) that thing, but may be expected of it owing to its
nature.
-Saying that man is “capable of education” or
KINDS OF DEFINITION “capable of a wise decision” is defining him by
1. Nominal Definition logical property.
- speaks about a term but not declaring
anything about it 3. Definition by cause- gives the factors that
contribute to the constitution of a thing as such.
Classification of Nominal Definition Four (4) causes that may be cited:
a. by Etymology – attained by tracing the origin of a. Definition by final cause- states the purpose
the term. of a thing.
Ex: Fraternity from “frater”, meaning “brother”. -Watch- “a mechanical device for telling time.”
b. by Description – attained by describing the term. b. Definition by efficient cause- states the origin
Ex: A rose is a flower. of or factor that produced the thing defined.
c. by Synonym – it is done by giving a word Man- may be said to be “a creature made by God.”
equivalent to the term. c. Definition by material cause- states the stuff or
Ex: Being kind is being benevolent material from which the thing is made.
d. Nominal Definition by Example –done by citing Nipa hut- is “a structure made of nipa and bamboo,”
anything that will represent the term. d. Definition by formal cause- states the form or
Ex.: Our Chief Executive is Benigno Simeon Aquino constitutive element that makes a thing what it is.
III. A man- may be defined as “an animal with a rational
soul,”
2. Real Definition
- declares something about the term; serves to RULES FOR A GOOD DEFINITION
explain about nature and to distinguish it from 1. Avoid circular definitions
other terms 2. Avoid too broad (inclusive)
Classification of Real Definition 3. Avoid too narrow (exclusive)
a. by Genus and Specific Difference- explains 4. Avoid vague, obscure, or metaphorical
the essence of a term by considering the language.
intelligible elements that make up the term. 5. Avoid loaded definitions
Ex.: A triangle is a figure with three sides. 6. Avoid negative terms.
“figure” – genus; “three sides” – specific 7. State the essential attributes
difference
LESSON 3: Proposition
b. by Description- stating the genus of the term
but altering the specific difference by giving the Proposition
logical property, which belongs to the term to - Based on judgment: declarative form; falsity or
be defined. truth, and affirmation and denial
Ex.: A Police Officer is a man bestowed with authority NATURE JUDGMENT OF A PROPOSITION
to enforce a law. 1. Aristotelian Proposition- all universal propositions
“man” – genus; “bestowed with authority to exist provided that subject exists in the real world
enforce a law” – logical property -all universal propositions have no existential import.
2.Boolean Proposition– advances the inexistence of
c. by Cause- by stating the genus of the term but universally accepted proposition
altering the specific difference by tracing its
cause. Elements of a Proposition
- A cause could be its purpose, function, reason 1. Subject term- refers to something affirmed or
for existence, make-up or origin. denied
Ex.: A book is a written material made-up of several 2. Predicate term – refers to what is affirmed or
pages and is a source of information. denied.
“written material” – genus; “a source of 3. Copula – a formal term that links the subject and
information” – cause or reason for existence predicate terms using either agreement or
disagreement.
EXAMPLE: Square is a plane 2.1. Categorical – it either affirms or denies
Square = the subject term; Plane = the something without any qualification or
predicate term; is = copula condition.
2.2. Conditional- it asserts something with
Properties of a Proposition qualification or condition. It can be disjunctive,
1. Qualitative –it is based on the copula used, either conjunctive and combination
negative or affirmative.
-Qualifiers: Kinds of Conditional Proposition
-Affirmative – is, are, were, can, have A. Disjunctive
-Negative – are not, were not, cannot, have - also known as alternative proposition, where it
not, no, none, never, etc allows two or more possible propositions to be
2. Quantitative – it is determined by the extension of formed, but only one will exist as true.
the subject term, either universal, particular, or - No two or more conditions will exist at the
singular. same time. It contains the disjunctions “ either,
● Universal Quantifiers - all, every, nothing, or”.
whoever, everybody, which ever - Example: Katrina is either dull or bright.
● Particular quantifiers – some, few, majority, Desiree is either a mechanical engineer or
most, many, several automotive mechanic
● Singular quantifier – it uses the copula term “
is” except if it follows after the universal B. Conjunctive
quantifiers regardless of the quantity of the - it contains two or more possible propositions
quantity of the predicate terms that follows. and which cannot exist to be true
simultaneously or altogether.
LESSON 3.1: Kinds of Proposition - Example: Dr. Smith cannot have an academic
ranks of a Professor and Asst. Professor in the
Kinds of Proposition University.
1. Simple– a.k.a attributive proposition where it simply
limits a statement to a specific characteristic or a thing. C. Combination
1.1. As to mode ( Affirmative or Negative) - it contains two or more proposition either or
1.2. As to quantity( Universal, Particular, both can be true.
Singular) - This contains the conjunctive or disjunctive
and ”either, neither, both.
2. Complex –allows the mind to think deeply on the - Example: Sam is either or neither or both an
possible alternative that is clear and definite.: electronics and computer engineering student.
hypothetical proposition.

L
ESSON 4: Categorical Proposition

Categorical Proposition
- proposition that relates 2 classes or categories
denoted respectively by the subject &
predicate term.
- asserts that either all part or part of the class
denoted by the subject term is included in or
excluded from the class denoted by the
predicate term

QUALITY, QUANTITY, AND DISTRIBUTION

PROPOSITION
CATEGORICAL PROPOSITION
PROPOSI Letter Quantity Quality Examples: Reality TV Stars hope for recognition.
TION Name All reality TV Stars are hoping for
recognition.
All S are P A Universal Affirmative Junk foods do not belong in school
cafeterias.
No S are E Universal Negative No junk foods are belonging in school
P cafeterias.
Not all romances have a happy ending.
Some S I Particular Affirmative Some romances are not a happy ending.
are P
DISTRIBUTION OF TERMS
Some S O Particular Negative - Distribution is an attribute of the terms (subject
are not P and predicate) of propositions.
- A term is distributed if the proposition makes
an assertion about every member of the class
 denoted by the term; otherwise, it is Elaboration of the Distribution of Terms
undistributed.
● "All S are P" S distributed
- if the statement assigns (or
distributes) an attribute to every
member of the class denoted by the
term.

Thus, if a statement asserts something about every

member of the S class, then S is distributed; if it
asserts something about every member of the P class ● "No S are P" S & P are
then P is distributed, otherwise S & P are distributed distributed
QUALITY,

QUANTITY, AND DISTRIBUTION PROPOSITION

MEANING IN CLASS NOTATION
PROPO MEANING IN CLASS NOTATION ● "Some S are P" Neither S nor
SITION P is
distributed.
All S Every member of the S class is a
are P member of the P class; that is, the S
class is included in the P class

No S No member of the S class is a member

are P of the P class; that is, the S class is ● “Some S are not P ” P is
excluded from the P class distributed
and S is
Some S At least one member of the S class is a undistributed.
are P member of the P class

Some S At least one member of the S class is not

are not a member of the P class
P
Elaboration of the Categorical Propositions in
Venn Diagram
DISTRIBUTION OF TERMS
Difference between the Boolean standpoint and the
PROPO Letter Quantity Quality Terms Aristotelian standpoint:
SITION Name Distribut
ed
Aristotelian Standpoint Boolean Standpoint
All S are A Universal Affirmative S
P ● concerned with ● universal
universal (A and propositions
No S are E Universal Negative S and P E) propositions have no
P ● universal existential
propositions import
Some S I Particular Affirmative None have existential
are P import when
their subject
Some S O Particular Negative P terms refer to
are not P actually existing
things

DISTRIBUTION OF TERMS (MNEMONIC DEVICES)

● Unprepared Students Never Pass (Universals Example:
distribute Subjects) “All raccoons are pests”
● (Negatives distribute Predicates) Boolean- does not imply the existence of
● Any Student Earning B’s Is Not On Probation anything
A distributes Subject
E distributes Both Aristotelian- implies the existence of raccoons.
I distributes Neither
O distributes Predicate
Thus, if we are to construct a Venn diagram to
represent such a statement from the Aristotelian
standpoint:

\The diagrams for the I and O statements are the same

from the Aristotelian standpoint as they are from the
Boolean:

● Contradictory means they have opposite truth

values.
● The other unlabelled relationships (like A to I,
E to O, etc.) are logically undetermined,
LESSON 5: MODERN AND TRADITIONAL meaning their truth values can’t be determined
SQUARE OF OPPOSITION by the relationship between them.

EXISTENTIAL IMPORTS IMMEDIATE INFERENCES (USING THE SQUARE)

● A claim that can be made based on a truth
value that you have about a proposition.
Boolean Standpoint Aristotelian
● They are “immediate” inferences because they
● All universals ● All universals have only one premise and lead directly to the
have no have existence conclusion.
existence provided that Examples:
regardless of the subject exist All people are happy. (A - true)
the existence of in the real world. Therefore, it is false that some people are not happy.
the subject or
(O - false) (All S are P),
validity.
therefore (It’s false that some S are not P).
● Claims from the Boolean standpoint are
BOOLEAN: unconditionally valid, since they are true
regardless of whether they refer to existing
things.
● Note that the conclusion in these examples is
not in standard form, but we fix that by simply
assuming that the statement itself is false and
inserting that truth value into the modern
square.
Example:
ARISTOTLE: “It’s false that some S are P” can be rephrased as
“Some S are P” is false.

● Some inferences aren’t as easy to figure out.

Example:
It is false that all people are happy. Therefore, no
MODERN SQUARE OF OPPOSITION people are happy.
• The relationship between these propositions – The premise is an A type and the conclusion is an E
contradict each other in several ways, as can be type. This inference doesn’t work since their
illustrated here. relationship is logically undetermined. Thus, this
inference is invalid.
IMMEDIATE INFERENCES (USING VENN No A are B. Therefore, it is false that All A are B.
DIAGRAMS) It is false that Some A are B. Therefore, Some A are
• To test inferences with Venn diagrams, we need to not B.
draw two circles, one for the premise and one for the - Example:
conclusion, then we illustrate the claims made in the ● All people are happy.
argument. ● Therefore, some people are happy.
Example:
- Some people are happy.
- Therefore, it is false that no people are happy.
We can see here that the argument is valid.

FINAL POINT
• A statement’s premises don’t have to be identical
with the conclusion, they just have to claim at least as
much as the conclusion.
SHOWING FALSITY
• To show falsity in a statement we do the exact TRADITIONAL SQUARE OF OPPOSITION
opposite of what is stated. • An arrangement of lines that illustrate logically
- Example: necessary relations among the four kinds of
● All S are P. categorical propositions.
● Therefore, it is false that no S are P. • It recognizes the additional factor of existential import
and supports more inferences that does the modern
square,

4 Relations in the Traditional Square of Opposition

may be characterized as follows:
● Contradictory- opposite true value
● Contrary - at least one is false( but not both
true)
● Subcontrary – at least one is true ( but cannot
be both false).
● Subalternation - truth follows downward, falsity
flow upward

EXISTENTIAL FALLACY
This is a type of fallacy committed when an argument
is made invalid because the claim in the premise
doesn’t have existential import.
All A are B. Therefore, Some A are B.
It is false that Some A are B. Therefore, it is false
that no A are B.
TRADITIONAL SQUARE OF OPPOSITION Therefore I and O propositions cannot be both false ,
1. Contradictory Relation but they can be both true.
● It is the same as that found in the modern
square. TESTING INFERENCE
● If A proposition is true, the corresponding O When an I proposition transmits Truthness, the O
proposition is false, or vice versa. proposition will become logically undetermined. Thus,
● The same relation holds between E and I the inference is invalid since it will commit a formal
propositions. fallacy, illicit subcontrary.
● The contradictory relation thus expresses
Some S are P is true. Some S are not P is
complete opposition between propositions
● Therefore, true.
If A is If O is If I is True, If E is Some S are not ● Therefore,
True, O is True, A is E is False True, I is P. Some S are P.
False False False
4. Sub-alternation Relation
2. Contrary relations ● represented by two arrows: a downward arrow
● It differs from the contradictory in that it marked with letter T(true) and an upward
expresses only partial opposition arrow marked with an F(false)
● If an A proposition is given as true, the ● The downward arrow only transmit only
corresponding E proposition is False (at least TRUTH and an upward arrow only FALSITY
must be false) ○ If A proposition is given as TRUE, I
● If an E proposition is given as true, the proposition is also TRUE
corresponding A proposition is False ○ If I proposition is given as FALSE, A
● But if an A proposition is given as False, the proposition is also FALSE
corresponding E proposition be could either be ○ If an A proposition is given as FALSE,
true or false without violating the “at least one the truth value cannot be transmitted
is false rule. downdard, so I proposition will have a
In this case, E has LOGICALLY UNDETERMINED logically undetermined truth value.
TRUTH VALUE.
● Similarly, if an E proposition is False, the TESTING INFERENCE
corresponding A proposition has logically A formal fallacy, illicit subalternation, is committed if the
undetermined value. movement downward transmit falsity
● Therefore A & E propositions cannot be both while upward transmit truthness. Thus, the inference
True, but they can be both FALSE will become invalid.
Form of the fallacy below:
TESTING INFERENCE
All S are P is false Some S are P is True.
When an A proposition transmits Falsity the E
● Therefore, ● Thus, All S are
proposition will become logically undetermined. Thus,
Some S are P P.
the
No S are P is false. Some S are not P is
inference is invalid as it commits a formal fallacy, Illicit
● Therefore, true.
contrary. To illustrate:
Some S are not ● Therefore, No S
All S are P is false No S are P is false. P. are P.
● Therefore, No S ● Therefore, All S
are P. are P
EXISTENTIAL FALLACY IN ARISTOTELIAN
3. Subcontrary relation – it also expresses a kind of ● According to the existential fallacy, it is only
partial opposition. committed in the Aristotelian Standpoint only
● If I is given as False, the corresponding O when drawing a conclusion from a premise
proposition is true (because at least one must that has no existence on the contrary,
be T). subcontrary, and subalternation. The fallacy is
● If O opposition is given as False, the never committed in contradictory regardless of
corresponding I proposition is True existence.
● But either an I or and O is given as true, then
the corresponding I proposition could be either An example of the existential fallacy in Aristotelian is:
True or False without violating the ”at least one All unicorns are one-horned animals
is true” rule. Thus, No unicorns are one-horned animals.
● Thus the corresponding proposition would
have logically undetermined truth value.
 IF THEN

TRUE TRUE FALSE UNDE

A I E&O

E O A&I

I E A&O

O A E&I

FALSE TRUE FALSE UNDE

A O E&I

E I A&O

I E&O A

O A&I E

NOTE:

IF ARGUMENT IS INVALID, THEREFORE IT

COMMITTED EXISTENTIAL FALLACY.

Invalid Boolean:
IF:
- Universal; true - existential fallacy
- Universal; false - no existential
- Particular; true - no existential
- Particular; false - existential fallacy