PHL - Critical Thinking I
Reasoning and Critical Thinking (Chapter 1)
The ability to reason is the fundamental characteristic of human beings. Virtually every conscious human
activity involves reasoning. We reason about everything from the meaning of life to what to have for dinner. Much of
the time we are not engaged in conscious reasoning, often we simply listen to what others say, take note of things
around us, experience feelings, daydreams and so forth. To understand reasoning properly, however, we need to
understand how it differs from mere thinking. When we are merely thinking, our thoughts simply come to us, one after
another; when we reason, we actively link thoughts together in such a way that we believe one thought provides
support for another thought.
The active process of reasoning is termed inference. Inference involves a special
relationship between different thoughts: when we infer B from A, we move from A to B
because we believe that A supports or justifies or makes it reasonable to believe in the truth
Inference indicators are words that are used to indicate that one thought is
intended to support another thought. It is important to note that sometimes the inference
indicator is missing; this can occur when a speaker thinks the inference is quite obvious.
The presence of an inference indicator is not important. What is important is the relationship
of support between the thoughts of the speaker. This relationship is a defining condition of
an inference; if two thoughts are linked by such a relationship they constitute an inference,
otherwise they do not.
When we express an inference in words, we do so by means of statements. A
Statement is a sentence that is used to make a claim that is capable of being true or false.
If a sentence is not capable of being true or false, then it is not a statement. Questions and
commands are not capable of being true or false therefore they are not statements. When
an inference is expressed in statements, it is called an argument. An Argument is a set of
statements that claims one or more of those statements, called the Premises, support
another of them, called the Conclusion. Thus, every argument claims that its premises
support its conclusion.
The Concept of Logical Strength
Since a statement makes a claim that can be true or false, any statement can be assessed by asking
whether it is true or false. When we assess the truth or falsity of a statement, it makes no difference whether or not it
is part of an argument. A statement that is part of an argument is assessed the same way as one that is not. To
discover the truth or falsity of statements we examine the statement itself and look for evidence that will show us
whether it is true or false. Assessing an argument is more complex than assessing an isolated statement. Since an
argument always includes a claim that its premises support its conclusion, assessing an argument means assessing
We say that an argument has Logical Strength when its premises, if true, actually
provide support for its conclusion. The concept of logical strength is central in critical
thinking and has two important features to be stressed. First, the logical strength of an
argument is independent of the truth or falsity of its premises: we do not need to know that
the premises of an argument are true in order to assess its logical strength. When we
assess the logical strength of an argument, we are really asking, If the premises are true
would we be justified in accepting the conclusion? And we can answer this question without
knowing whether or not the premises are actually true.
Second, the logical strength of an argument is often a matter of degree. Some
arguments are so strong that the truth of the premises guarantees the truth of the
conclusion. These arguments are called Deductive Arguments, and they constitute strict
proofs. But most arguments are not as strong as this; usually, the truth of the premises makes it reasonable to hold that the conclusion is also true, but does not provide an
absolute guarantee. Such arguments are called Inductive Arguments.
Truth, Logical Strength, and Soundness
An argument that has both logical strength and true premises is called a Sound
Argument. It is very important to be aware of the differences among these three properties.
Truth is a property of statements and never of inferences. Logical strength is a property of
inferences and never of statements. Logical strength refers to the inferential connection
between the premises and the conclusion of an argument. Soundness is a property of an
argument as a whole. Always keep the question of strength separate from the question of
truth when dealing with any argument. Never simply ask, Is this a good argument? Ask two
(1) Is this a logically strong argument? And
(2) Are its premises true?
There are even times when we want to develop an argument with premises that we
know or assume to be false. Such arguments are called Counterfactual Arguments
because at least one premise is a counterfactual statement. We should also note a special
kind of counterfactual argument called the Reductio Ad Absurdum. In a reductio
argument, a statement is proven to be true by assuming it to be false and then deriving a
contradiction from that assumption.
Meaning and Definition (Chapter 2)
Reasoning, we have said, involves thinking. Thinking, in turn, involves language, for without language we
could not express (and probably not even have) thoughts. In order to understand reasoning, therefore, it is necessary
to pay careful attention to the relationship between thought and language.
The complexity of Language
Language is an extremely complex phenomenon. Language takes practise to understand, there are many
different ways to say the same thing. Written and spoken language, although closely connected, are nevertheless not
identical: spoken language is more flexible (and hence more complex) than written language, for we can change the
meanings of words and sentences through gestures, tone of voice, and facial expressions. Understanding spoken
language, therefore, requires much more than knowing the written language.
The Meaning of Language
Usually it is not difficult to explain what a particular word or sentence means. But there is much that is
puzzling about the nature of meaning itself. There are three theories of meaning. The first two are common-sense
views that have been told by many people, including many philosophers and linguistic theorists. Unfortunately, both
are open to objections, and many philosophers now regard them as untenable. The third theory avoids the weakness
of the first two and is the one that will be used.
Reference theory of meaning is the theory that we associate the meaning of
words with images in our heads of the certain word. At the heart of the theory there
seems to be a confusion between understanding the meaning of a word and having
knowledge of what the word refers to. When we understand the meaning of the word
dog, we usually have knowledge of only a small proportion of the dogs that exist, and
this is puzzling if the meaning of dog is the reference class of the term. For example, we
all understand the meaning of the phrase the oldest man in the world, even when we
don’t know to whom it refers. If the meaning is the reference, then we shouldn’t be able
to understand what the phrase means unless we know who the oldest man in the world
is. The reference theory therefore has to be rejected.
Idea Theory of Meaning was developed by John Locke in the seventeenth
century. He held that the meaning of a word consists of the idea or mental image that is associated with the word. The idea theory also encounters several difficulties. Just as
the class of unlesses seems to make no sense, the mental image of the word unless
seems to make no sense. A difficulty with the idea theory is that it has the consequence
that we can never know what another person means by certain words. You can never
see my mental images and I can never see yours. If the mental image is the meaning of
the word, then how can you know what I mean when I say certain words like dog.
Meaning as Use is the theory that words only have meanings only when they
are used in sentences: without such a context they have no meaning. This theory
recognizes that many words do refer to things and that many words have mental
images or ideas associated with them.
The Main Functions of Language (Purposes of Language)
Descriptive: An important use of language if to describe (i.e. to convey
factual information about) something. Whenever we describe something we are stating
facts, or what we believe to be facts.
Evaluative: We use language often to evaluate or make a value judgement
Emotive: Language is sometimes used to express emotions and thus has an
emotive function. For example, when you say, “I hate this teacher” you are expressing your
hatred toward the teacher. Note: these sentences also convey factual information about the
speakers’ feelings, but in most contexts this function would be secondary.
Evocative: Language can also be used for the purpose of evoking or bringing
out certain feelings or emotions out of your audience. Many others uses of language can
often be evocative as a secondary function. For example, the interrogative use of language
can bring out feelings of fear. (e.g. when an officer orders you to give your information or
else he will arrest you, he is using language in three ways, interrogative because he is
seeking information, directive because he is ordering you to give your information, and
evocative because he is asserting his authority over you in order to instill fear.)
Persuasive: One of the most widespread uses of language is to persuade
people to accept something or to act in a certain way.
Interrogative: In order to elicit information we usually need to ask for it. This
does not need to be a question, it is just a use of language where we are seeking to gain
Directive: We use language to command others to do something or to
Performative: This use of language, when used under appropriate
circumstances, each would constitute an action. For example, when a judge says, “I find the
accused guilty of murder”. This sentence can constitute the action of finding someone guilty
Recreational: The last use of language is used to amuse ourselves and
others. Examples of a recreational use would be to tell jokes, write novels, invent puns, do
crossword puzzles, play guessing games, make up limericks, sing nursing rhymes, and
write rude things on the bathroom walls. When people use language in a recreational way
they are simply doing to get enjoyment out of language.
The way we use language can always fit into either one or more of the categories
provided. Purposes of Definition
Reportive Definition: The most common purpose of definitions is to convey the information
needed to use a word correctly. The correct use of a words consists of its standard usage –
how the word is in fact used by those who make regular use of it. Standard, desktop
dictionaries give reportive definitions. Reportive definitions can sometimes be troublesome
because it may not be clear whether or not a certain use of a word is regarded as standard
usage. When a word is used incorrectly enough times, for example, it will become the
Basically any word’s definition that is used constantly and has become the standard usage
for the word.
e.g. common words like dog, car, school, etc.
Stipulative Definition: Sometimes it is useful to be able to create a new precise meaning
for a word. For example, when doing research we need to stipulate the precise meaning of
a word in order to have clarity and precision. The stipulative meaning must be clearly stated
in order for there to be no confusion as to the meaning of the word.
Basically any word’s definition that is created for a specific purpose and is outlined with
clarity and precision.
e.g. words that are used in scientific cases and in law
Essentialist Definition: These definitions need to be understood as compressed theories.
These definitions attempt to express in a brief form a theory about the nature of what
exactly is being defined. Therefore when you are taking in an essentialist definition you
must assess a theory and this goes far beyond question about the meaning of words.
Basically any word’s definition that takes on an entire theory in order to define the word.
e.g. words like justice, faith, hope, etc.
Methods of Definition
Genus-Species: A common method of defining words by referring to a larger
category to which that kind of thing belongs to and then to specify what makes that
particular kind different from other species in that genus.
Ostensive: The meaning of a word can easily be conveyed by giving examples,
either verbally or by pointing.
Operational: a term can be defined very precisely by specifying a rule of operation.
Synonym: Often all that is needed to define a word is to give a similar word.
Contextual: Some words can be defined by using the word in a standard context
and providing a different sentence that does not use the word but has the same meaning.
Assessing Reportive Definitions
Too Broad: when the defining phrase refers to things that are not included in the reference
of the term being defined. Too Narrow: when the defining phrase fails to refer to some things that are included in the
reference of the term being defined.
Too Broad and Too Narrow: when the defining phrases refers to some things to which the
term does not and also fails to refer to some things to which the term does.
Circular: is a definition where it includes the word being defined.
Obscure: A definition can also be useless when it fails, through the use of vague, obscure,
or metaphorical language, to express clearly the meaning of the term being defined.
Clarifying Meaning (Chapter 3)
The Principle of Charity
In any discussion we have a moral obligation to treat our opponents fairly. When they are
present, we ought to give them the opportunity to clarify what they have said. When they
are not present, we have a moral obligation to follow the principle of charity, that is, to adopt
the most charitable interpretation of their words among the possible interpretations
suggested by the context. The most charitable interpretation is the one that makes our
opponent’s views as reasonable, plausible, or defensive as possible, we should always
adopt the more reasonable one (unless something in the context suggests that another
interpretation is what the person meant.).
Ambiguity and Vagueness
An ambiguous sentence is one that has two or more different but possibly quite precise
meanings. A vague sentence is one that lacks a precise meaning.
Ambiguous – two or more possible meanings
Vague- Lacks a precise meaning
Referential Ambiguity arises when a word or phrase could, in the context of a particular
sentence, refer to two or more properties or things. Usually the context tells us which
meaning is intended, but, when it doesn’t, we may choose the wrong meaning.
Tom gave Ted’s skis to his sister.
Pavarotti was a big opera star.
When a word refers to more than one thing in the same context Grammatical Ambiguity
Grammatical Ambiguity arises when the grammatical structure of a sentence allows two
interpretations, each of which gives rise to a different meaning.
Women with babies who attend university encounter all sorts of exceptional challenges.
Use and Mention
Another type of linguistic ambiguity arises through the failure to distinguish between using a
word or phrase and mentioning a word or phrase.
Tom said I was angry.
Tom said, “I was angry.”
Analytic, Contradictory, and Synthetic Statements
A statement that is true by definition is called an Analytic statement.
A statement that is false by definition is called a Contradictory statement.
A statement whose truth or falsity is not solely dependent upon the meanings of the words
in it is called a Synthetic statement.
All statements can be placed in one of these three categories.
Descriptive and Evaluative Meaning
Most words have a Descriptive and Evaluative meaning to them. A descriptive meaning
though does not try to evaluate what is being described.
Fritz Kreisler was a renowned violinist. This is both an evaluative and descriptive because it
offers both the opinion of the speaker, which is that he is a very good violinist, and the fact
that he was a well-known violinist.
Fritz Kreisler was a well-known violinist. This has just a descriptive meaning as it just states
that Kreisler was a well-known violinist.
Fritz Kreisler was a notorious violinist. This is also both an evaluative and descriptive
because it offers the fact that he was a well-known violinist, and a negative opinion about
Necessary and Sufficient Conditions
A special kind of ambiguity can arise when talking about the conditions that have to be met
in order for a claim to be true or for something to occur. We call these conditions antecedent
conditions, and the outcome or resultant state is called the consequent.
There are two types of conditions – necessary and sufficient.
A necessary condition is defined as follows: X is a necessary condition for Y if, and only if,
when X is false Y must also be false. In other words, unless the necessary condition X is true, Y will not be true; but the truth of X does not guarantee the truth of Y.
A sufficient condition is defined as follows: X is a sufficient condition for Y if, and only if,
when X is true Y must also be true (or, when X is present Y must occur). In other words, a
sufficient condition for Y is something whose truth or presence guarantees Y, but whose
falsity or absence does not prevent Y.
Reconstructing Arguments (Ch.4)
Before we can critically asses an argument, we have to determine what the actual argument
is. What its conclusion, what are its premises, and what is the precise relationship between
them? The process of eliciting this information is called reconstructing the argument.
1. The conclusion is underlined and labelled by C.
2. Premises are enclosed in brackets and labelled by P1, P2, P3, etc.
3. A missing premise or conclusion is labelled by MPx and MC.
The first step is to identify the conclusion. What is the author’s main point? What is the
author trying to get the reader to accept?
The second step is to identify the premises. What reasons does the author present to
support the conclusion?
Before moving to the second phase in reconstructing an argument, that is, identifying its
structure, we need to consider how to deal with missing premises and conclusions.
Missing Premises and Conclusions
The principle of charity requires us to consider whether something is missing. If the author
is not present, we have to use whatever knowledge we possess and whatever clues the
context provides to supply a missing premise that makes the best sense of the argument. If
we lack the knowledge that would allow us to supply the missing premise, we can only
make a tentative assessment of it.
Sometimes we encounter passages which contain arguments but are not arguments
themselves. These are called reports of arguments.
Reports of Arguments
A report of an argument is a statement that says that so-and-so argued in a certain way. A
report of an argument is no more an argument than a photograph of an accident is itself an
accident. Of course, since it is a statement, we can ask whether or not it is true, that is, if it
correctly reports some facts about whatever they are talking about. Explanations
The second kind of special case consists of explanations or explanatory arguments. An
explanation is an attempt to show why or how something happens (or has happened) when
there is little reason to doubt the truth of the conclusion.
There are several different types of explanations. Many explanations are casual: they
explain an event by reference to its causes. But some explanations are non-casual. The
purpose of an explanation is to make explicit why or how some phenomenon occurred or
some event happened; as we said above, explanations are appropriate when the event in
question is taken for granted and we are seeking to understand why it occurred.
The Structure of Arguments
The simplest type of argument consists of a single premise and a single conclusion. Such
arguments have a structure that we will call a simple argument.
When we consider arguments with two premises, there are two possible structures the
argument might have, and it is important to be aware of how they differ.
In a T argument each premise provides little or no support for the conclusion if it is
considered by itself. The premises support each other in order to support the conclusion
T Argument may have three or more premises as well.
P1 P2 P3
The third basic structure for argument offers two separate reasons to support the
conclusion. Each premise independently supports the conclusion.
P1 P2 C
Just like T arguments V arguments can also have more than two premises to support the
P1 P2 P3
A complex argument often uses a sub-conclusion to support the real conclusion
In reality, there are two arguments here; P2 is the conclusion of the first argument and the
premise of the second. The first argument is P1 therefore P2, and the second is P2
therefore C. The combined argument does not, however, present two separate reasons to
support the conclusion, but only one. A complex argument can be made up of V and T
People talk about all sorts of thing for all sorts of reasons. Sometimes we can be fooled into
interpreting something as an argument when it really isn’t. Sometimes people use language
that makes it appear that they are presenting an argument when they are really just
expressing a strongly held opinion and not attempting to defend it with reasons. Since we
are sometimes entitled to supply missing premises and missing conclusions, we may be
tempted to turn a non-argument into an argument by reading a great deal more into the
passage than there really is. When dealing with a doubtful passage we should therefore be
careful not to assume that it must be an argument, or we may find ourselves reconstructing
an argument that the author never intended.
The test takes most of the stuff from the chapters we already did, we have to be kinds of language use, definitions, kinds of definitions, different types of definitions. Be able to
reconstruct an argument.
Strategies for Assessing Arguments (Ch.5)
Every argument supports its conclusion by making a double claim: that its premises are true
and that its premises support its conclusion. Whenever we assess an argument, we are
really only asking whether these claims are true. An argument makes a kind of promise;
assessing an argument is asking whether it can make good on its promise.
Philosophers have developed two approaches for assessing arguments. The first is the
fallacies approach, in which we identify all the specific fallacies (or mistakes) that an
argument can make and then ask whether a given argument commits any of these fallacies.
If it commits none of them, it will be a good argument, and if it commits one or more of
them, it will be a bad argument. The second is the criterial approach in which we appeal to
the criteria, or standards, that a good argument must satisfy and ask whether a given
argument meets these criteria. If it meets all of them, it will be a good argument, if it fails to
meet one or more of them, it will be a bad argument.
The Fallacies Approach
The concept of a fallacy presents several theoretical difficulties for logicians that need not
detain us here. For our purposes we can define a fallacy as any error or weakness that
detaches from the soundness of an argument, yet somehow manages to disguise this
weakness so as to give the argument the appearance of being better than it really is. For
example sometimes we use emotions to appeal to others without actually having a good
argument for something. The underlying problem with the fallacies approach is that it is
negative in nature. This is an especially serious problem when we are trying to develop
good arguments for ourselves, rather than merely criticizing other people’s arguments.
The Criterial Approach
This approach is positive in nature. It begins by establishing the criteria that a good
argument must satisfy and then uses these criteria as a basis for assessing particular
arguments. To develop these criteria we rely directly upon the concept of a sound
The Three Criteria of a Sound Argument
The requirement that a sound argument must have true premises is the basis for our first
criterion for a sound argument: it should have true premises. Obviously, since premises are
offered as support for a conclusion, if a premise is false, then no matter how good the
argument is in other respects, the premise provides no support for the conclusion. But
because it is often hard to prove that our premises are true, our first criteria, therefore, is
that the premises must be acceptable. Logical strength, the second requirement for a sound
argument, gives rise to our second and third criteria. The second is that the premises must
be relevant to the conclusion. The third is that the premises must be adequate to support
the conclusion. The three rules are:
1. The premises must be acceptable.
2. The premises must be relevant.
3. The premises must be adequate.
Seven Rules for Assessing Arguments
Rule 1 Identify the Main Conclusion
First, Look for the main point of the passage, by asking, What is the author driving at?
Second, Look for the inference indicators, such as therefore, hence, so, consequently, and
Third, Pay attention to the context and background for clues as to what the argument is all
Fourth, Bear in mind the principle of charity when interpreting an ambiguous conclusion or
when supplying a missing conclusion.
Rule 2 Identify the Premises
What information or reasons does the author provide to support the conclusion?
Rule 3 Identify the structure of the Argument
Once the conclusion and the premises have been identified the structure of the argument
must be identified. If necessary you can draw a diagram of the structure.
Rule 4 Check the Acceptability of the Premises
If the argument is meant to be a counterfactual argument, it is irrelevant to ask whether that
premises are true, since the author is not claiming they are true. We need to note that a
false premise does not always deprive the conclusion of all support.
Rule 5 Check the Relevance of the Premises
It should be stressed that the premises must be considered in context, for a premise that is
irrelevant when considered