Philosophy and Logic Essay Writing
Introduction to Philosophy PHIL 1200 Unit 1 1
Unit 1
Introduction to Philosophy
Introduction
To act without clear understanding, to form habits without investigation, to follow a path all one’s
life without knowing where it really leads—such is the behaviour of the multitude. (Meng-Tse)
Many people would sooner die than think. In fact they do. (Bertrand Russell)
This unit has two distinct sections designed to acquaint you with the nature of philosophical
reasoning:
The first part contains:
• a brief characterization of philosophy;
• a discussion of the attitudes that are important to doing philosophy;
• an explanation of the value of philosophy; and
• an explanation of the relationship between philosophy and other fields of theoretical inquiry.
The second part is an introduction to logic.
Learning objectives
Upon completion of this unit, you should be able to:
1. outline the basic methodology of philosophy;
2. describe the basic intellectual attitudes necessary for being a good philosopher; and
3. outline the basic concepts and rules of logic.
Assigned reading/viewing/listening
1. Plato, Socrates’ defence (Apology) – http://classics.mit.edu/Plato/apology.html Apology by Plato
translated by Benjamin Jowett
2. Sober, Elliot. 2001. Deductive arguments and inductive and abductive arguments. In Core
questions in philosophy, 3rd ed., 7-34. New Jersey: Prentice-Hall.
ON RESERVE from Off-Campus Library Services.
3. Crossley, David J., and Peter A. Wilson. 1979. Don’t let them fool you: Some common fallacies.
In How to argue: An introduction to logical thinking, 39-52, 236-237. New York: McGraw Hill.
Available in your readings package
4. Crossley, David J., and Peter A. Wilson. 1979. Some perplexing arguments: The dilemma and
the reduction. In How to argue: An introduction to logical thinking, 151-168, 257-259. New York:
McGraw Hill.
Available in your readings package
Required viewing (linked in the instructional content)
Examined Life Video: What is Philosophy?
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Learning activities
Discussion overview
When you are ready to become involved with the discussions, access the discussion area for Unit 1
in your course web site. Other students will then post feedback about your points, questions for
clarification, or additional statements to add to your original argument. If you want to respond to
another student’s comments, you can do so by selecting the reply option.
The central purpose of the discussion will be to develop the theme of “moving the discussion along”
even if it involves asking another question that simply rewords the original or perhaps one that
changes the approach to an answer. To this end of ‘moving the discussion along’ you may want to
engage with one of the questions you saw in the self-tests – especially the questions that didn’t have
an automatic response provided. In any case, you may find that those self-test questions take on a
new relevance when you run into them again during your online discussions.
Once discussion of one unit has been completed, you are ready to go on to the next unit.
In each unit you will see, “Intuition pumps” used as motivating questions. These questions are
intended to get at our “gut feeling” about our answer to a certain question. That is, once we strip
away all assumptions and personal investment in a response to a question what is our answer?
Some regard this, colloquially, as getting to the heart of the matter.
Your answers to the questions will not be graded, they are provided to give opportunities to help you
understand the concepts in the unit rather than just trying to memorize them. Therefore, while there
is no initial grade assigned to these exercises, doing them should help in attaining the overall grade
you desire for this course.
It is important to note that your instructor will not respond to each posting. Your instructor will oversee
the discussions and periodically join in to help guide and facilitate them when necessary. The
general goal of these exercises is for you to start and build a discussion with your classmates based
on the questions asked in the course manual.
Discussion focus
• This unit and this course start with discussing the nature of a
philosophical question. This is motivated by asking: what was Socrates
doing in his day, and then using that as an example of what philosophy is
doing today.
Question: What characterizes a philosophical question?
How to proceed
• Complete your readings and view the online videos. Overall, the best approach to this
introductory unit is to deal with it in two parts.
• Participate in the online discussion. Remember, each unit has a particular focus for the
discussions.
Part 1
1. Read the sections “What philosophy is” and “Areas to be studied” in the instructional content for
this unit.
2. Links to video clips are inserted throughout the instructional content. View each video when it
occurs in the instructional content.
3. Read Socrates’ Defence (Apology) by Plato in your required readings.
Introduction to Philosophy PHIL 1200 Unit 1 3
Suggestion:
Make careful notes on the Plato reading as the first
assignment will require you to refer to it in some detail.
Part 2
4. Read the section “A brief introduction to logic” in the instructional content.
5. Links to video clips are inserted throughout the instructional content. View each video when it
occurs in the instructional content.
6. Read “Deductive Arguments” and “Inductive and Abductive Arguments” by Elliot Sober in the
required readings.
7. Now that you have participated in the online discussion, completed your readings, and viewed
the video clips, prepare for and work on your assignment by completing the following:
a. Do the online self-test questions and check your responses against the answers provided.
b. A glossary of key terms is provided in the online course; consult it whenever you are unsure
about the meaning of a technical term.
c. Complete the unit assignment and submit it online. Be sure to submit the honesty
declaration when you submit assignment 1.
Instructional content
What philosophy is
Philosophy is not an unsystematic, disorganized, free association of ideas strung together in an
attempt to find some “hidden” truth, or an attempt to satisfy some need to “let it all hang out.”
Students who take a course in philosophy because they believe it to be an opportunity to obtain a
good grade for a minimal amount of work are inevitably disappointed. They seem to feel that,
because they have a good imagination and a great deal to say, or perhaps because they are good at
getting the last word in arguments with their friends, they are already good philosophers. Typically,
these students do little work yet are surprised at how poorly they do on their assignments.
You should no more expect to be good at philosophy without studying and practising it than you
should expect to be a good doctor without studying and practising medicine. Philosophy can be fun,
but it is first and foremost an academic discipline with stringent standards. Remember, you have to
be able to defend your philosophical views. How well they stand up to criticism is a mark of how well
you do philosophy. In this course you are going to find that you have to present arguments for certain
points of view, and that these arguments will be criticized as to how well-reasoned they are. This
course is not a presentation of facts to be memorized. You should grapple with the issues and arrive
at your own conclusions.
Required viewing
Examined Life Video – What is Philosophy? [Length: 30 minutes]
©1998. INTELECOM Intelligent Communications. All rights reserved. No alteration, duplication or downloading is permitted
with authorization. Reproduced with permission from Distribution Access.
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A characterization of philosophy
Philosophy is quite different from all other fields, but the differences are complex and somewhat
difficult to specify. Indeed, “What is philosophy?” is itself an important philosophical question, one
that divides philosophers at least as much as any other. However, we can give a rough description of
philosophy.
Let us briefly consider the history of philosophy. At one time what was called philosophy
encompassed all fields of theoretical inquiry (including physics, chemistry, and psychology). As
inquiry proceeded, one by one each field reached a point where there was one or perhaps two,
dominant theories, and a more or less accepted empirical decision procedure or methodology for
answering questions within the field. An empirical methodology is one that settles questions through
the use of observation. Once a field becomes empirical, it has moved away from philosophy and
becomes a discipline unto its own (a recent example is the field of psychology). Historically then, the
last philosopher to study a particular area, is often better known as the founder of a new field; for
instance, Isaac Newton would have considered himself a philosopher, but we know him today as a
physicist.
Although the fields that have left philosophy still rely upon philosophical methodology (debate) to
some extent, there is clearly in each case an emphasis upon scientific or empirical methodology.
These fields, unlike philosophy, are said to depend upon empirical data or testing for solving their
problems. Philosophy itself depends upon empirical data or tests for the solution of some of its
questions (this should not be too surprising for a field that has spawned so many empirical
sciences), but by and large it does not. Rather, questions are debated (and solved or not solved) by
the dialectical process whereby arguments are advanced on each side of an issue. Perhaps that is
the one question that all philosophers will answer in the same way: the methodology of philosophy is
argument and counter-argument. To put it simply, philosophers debate within a field until the field is
dominated by one or two main theories and has developed a scientific or empirical methodology for
resolving questions. At that time, the field is likely to leave the domain of philosophy (perhaps taking
some philosophers with it and, in a sense, making them scientists). In other words, as philosophy is
successful, it loses some of its areas of inquiry to science. Thus far, apart from the reference to the
centrality of debate, not much has been said about the proper methodology of philosophy. Opinions
on this have varied, and still do. In some traditions, philosophy has been considered the search for
truths that are available to the human intellect independently of the making of observations. In this
century one philosophical movement considered that the task of philosophy is not to come out with
proposals (truths) of its own, but rather to use special techniques to critically analyze the proposals
(truths) of science. Another modern movement views philosophical problems (such as the problem
of whether we have real free will) as unnecessary wasteful conundrums brought about by taking the
structure of our language too seriously. From this standpoint the philosopher’s task is a form of
therapy, to show people how to avoid getting caught up in problems that seem profound and
important, but are not.
At this point a word of caution is in order. Many students find these facts discouraging. Students
often come to philosophy in the hope of obtaining answers to their philosophical questions, or to find
a ready-made and comprehensive world view. To their disappointment they find that philosophers
have not settled matters amongst themselves. In light of what has been said, this is inevitable since,
if the matter were settled, then it would no longer be a part of philosophy.
Doing philosophy requires patience and determination. Answers to philosophical questions are to be
had for individual philosophers, even though philosophers as a group are not united in their answers.
As a philosopher, one must be prepared to work on philosophical questions and to accept the
likelihood of playing only a minor role in their solution. (This is actually true for all those working on
the bigger questions in all theoretical fields of inquiry.) Philosophy, however, as a form of inquiry, is
very important, as can be understood by considering the fields it has spawned.
However—and this is the real value of philosophy for the individual—the study of philosophy leads to
a better understanding of issues (the existence of God, the nature of morality, the nature of
perception, and so forth), that as thinking beings we cannot ignore. The study of philosophy also
helps to gain a perspective on the sciences and arts at least to the extent that they are struggles to
deal with these same issues. The practical value of philosophy is that it makes one a much better
thinker, and hence better equipped to do work in other fields.
Introduction to Philosophy PHIL 1200 Unit 1 5
The critical task of philosophy
Philosophy is doubt. (Montaigne)
You will probably do much better as a philosopher if you are willing to reflect upon your own beliefs,
and if you are able to admit when you are wrong. As you read about Socrates try to get a feel for a
type of penetrating, open, and honest search for truth. Socrates was able to show that his
contemporaries did not really know what they thought they knew. He did so by asking questions
about matters fundamental to various subjects. A question is said to be fundamental to a subject if
one’s knowledge claims about that subject presuppose knowledge of an answer to that question.
The usefulness of such questioning as performed by Socrates is twofold: it can show us when we do
not know what we think we know, and it can help us see more clearly what we do in fact know. In
other words, by questioning that which is accepted implicitly, we bring to consciousness more of our
own world view. To achieve these two benefits, one has to admit when one has been wrong, and one
has to openly and honestly reflect upon one’s beliefs.
The conceptual analysis task of philosophy
William James used to preach the “will to believe.” For my part, . . . what is wanted is not the
will to believe, but the wish to find out, which is the exact opposite. (Bertrand Russell)
The critical task leads quite naturally into conceptual analysis. Philosophers are constantly asking
each other what is meant by a concept or principle. They are forever looking for counterexamples to
proposed definitions and principles. (The nature of principles and definitions will become much
clearer as we work our way through this course.) This is a point that presents some difficulties in
understanding for students new to philosophy.
When it comes to meanings, it is legitimate to entertain ideas that do not refer to any existing things
for the purpose of producing counterexamples to any proposed definition or principle. Some students
have trouble with this, but you should keep in mind that when a term is defined, the definition is
meant to apply to all conceivable situations (or possible examples) to which the term could be
applied, whether those situations exist or not. For example, in response to the question, What makes
an act a good act from the moral point of view?, philosopher A might reply: an act is morally good if it
is an act that leads to the greatest happiness for the greatest number. Philosopher B might criticize
this principle by concocting a logically possible case that he would expect all would take to be a
counterexample to the principle. For example, philosopher B might say of philosopher A’s principle
that this is not what we mean by acts being morally good, because if it were, then we would agree
that if most people took extreme happiness in the torture of one individual, then torturing that
individual would be morally good. Since Philosopher B expects us to agree that such torture would
be morally bad, he expects us to reject the principle proposed by philosopher A. This is so, since B
thinks it evident that his example falls under the principle proposed by Philosopher A. Philosopher A,
who first proposed the principle, may agree and reject his own principle, or he may argue that B’s
proposed counterexample only seems to fall under his proposed principle, but does not really, and
so is not a counterexample. The debate may continue in this manner for quite some time, moving
through a series of proposed definitions and counterexamples. It is important to notice, however, that
the debate has been of value even though it has not been resolved. In this case it has been of value
because it has shed further light on what we mean by a “morally good act.”
In philosophy much time is spent searching for a principle or definition that will fit all the logically
possible examples. It is appropriate therefore to devise new examples that we agree will fall under
the concept being defined. The examples serve as tests for our definition or principle, to see if we
have actually captured what we mean. Of course, not all conceptual analysis is like this (as
sometimes definitions and principles are rejected simply because they are vague or ambiguous), but
a great deal of conceptual analysis is done this way. We mention this because many students see
this method of thought experiment as being quite mystifying. However, keep in mind that it is quite
appropriate to a field like philosophy.
This type of conceptual analysis may also seem puzzling because it implies that we already know
what we mean, but in another sense implies that we do not. This is quite correct, as we implicitly
know our concepts because we know how to use them (otherwise we would not be able to tell which
logically possible examples fell under them and which did not). However, we do not explicitly know
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our concepts in the sense of being able to spell them out in the form of definitions or principles. The
articulation of our implicitly known concepts falls under the conceptual analysis task of philosophy.
Conceptual analysis yields knowledge in the sense of making explicit or articulate that which is only
known implicitly. But notice what kind of knowledge this is. It is knowledge of our concepts, but it
does not follow that our concepts are true, or that the principles we hold are those we ought to hold.
This type of analysis yields knowledge in another way, as when we discover that the concepts we
use daily are vague, ambiguous, indefensible, or incompatible with what has more evidence in its
favour. When this happens, we are forced to make a choice if we want a consistent and clearly
articulated world view. This of course leads to the constructive or speculative task of philosophy.
The constructive task of philosophy
What is the use of studying philosophy if all that it does for you is to enable you to talk with
some plausibility about some abstruse questions of logic, etc., and if it does not improve your
thinking about the important questions of everyday life .. ? (Ludwig Wittgenstein)
The constructive task can be characterized as the search for a consistent view as to how things, in
the broadest possible sense of that term (e.g., all things, including physical objects, ideas, pains,
human rights, morally good acts, etc.) hang together, in the broadest possible sense of that term.
(This is a paraphrase of Wilfrid Sellars’s characterization of philosophy.) In short, it is the search for
a consistent world view. But usually the constructive task is not so ambitious a project as an entire
world view. For example, a philosopher might present a system of morality he believes to be
consistent with all known moral codes, or a theory of physical objects that he believes to be
consistent with what we know about science, or a theory of how people ought to live that he believes
to be consistent with what we know about human nature.
Keeping in mind the concept of a world view with interconnected subject areas, try to find the
relationship between the subject matters of the different areas of this course. For example, if you
adopt current scientific method as a theory of knowledge for all subject matters, then you will have to
hold a view of ethics that is justifiable by current scientific method. If you are not careful, you might
unwittingly find yourself holding ethical beliefs that are incompatible with your theory of knowledge. In
this event you will have to change either your ethical beliefs or your theory of knowledge in order to
have a consistent world view. The point is, there are major themes running through the subject
matter of philosophy, such that what you assert in one area may have awkward consequences in
another.
To achieve a consistent outlook you must strive to discern the implications of any view you hold. This
will involve making the consequences of your theory explicit. It is considered bad philosophy to hide
awkward consequences or weak spots of a theory. Of course, we do care which views you support
(we are interested in truth after all), but as philosophers our concerns are usually with good
arguments. After all, philosophers believe that good arguments are the means by which we will find
the truth. Thus, if you can present strong arguments for a novel view, then you can get a top grade
just as easily as can the person who presents equally strong arguments for a “standard” view. But in
both cases, you should make explicit that which is significant and entailed by your view. If your view
is defensible but entails the significant fact that the earth is flat, then be explicit that your view entails
that the world is flat. (You will soon encounter many seemingly “crazy” views that made some
philosophers famous and widely respected. (Some of the views that we dearly hold now were once
viewed as “crazy” views.) One of the reasons for taking a philosophy course is to acquire the ability
to be honest in what your own views entail, and to develop skills for seeing how some beliefs entail
other beliefs. The history of ideas is replete with cases where great discoveries could have been
made, but were not because no one drew the right, and sometimes obvious, implications.
Philosophy is a search for truth, of course, but it is also a discipline where alternative world views
and theories are worked out in all their implications. In our search to explain the world, we need
different world views in our conceptual tool box, as it were, ready for use should a current world view
be judged inadequate. For example, materialism (the view that a person is entirely physical as
opposed to being both physical and spiritual) was not widely accepted until this century. Yet
philosophers have been developing the logic of materialism since the early Greeks. Thus, the
implications of materialism as a theory were already available before the many philosophers and
Introduction to Philosophy PHIL 1200 Unit 1 7
scientists of this century came to believe that dualism (the view that people are a composite of
physical bodies and nonphysical minds) should be rejected. This meant that the philosophical work
(including the debates) on materialism that took place over history have proved useful in this century,
even though that may have seemed unlikely when they occurred. We do not know beforehand which
theoretical turn our world views will take, but we do know that unless we have theoretical alternatives
worked out we will be stuck with our existing world views and their deficiencies. A consistent and
well-developed world view cannot be constructed overnight, but must be developed over a long
period of debate and research.
Areas to be studied
Logic
We have emphasized the point that argumentation is central to philosophy. Logic helps us to distinguish
good arguments from bad arguments. Logic is not an infallible antidote to sloppy reasoning, but provides
techniques that help us to discover inconsistencies, unacceptable inferences, and problematic premises
in arguments. Some of the questions we will examine are:
What is an argument?
What criteria distinguish a good argument from a bad argument?
If an opinion is supported by true premises, must we accept it?
What reason do we have for rejecting arguments that contain inconsistent premises?
Epistemology
It is commonly believed that we know many things on the basis of perception, that we know about the
mental states of other people through knowledge of their behaviour, and that we know there is a
physical world that is analyzed by science into its basic elements. Epistemology is the study of the
nature and rationality of these and other knowledge claims. It is an attempt to determine what we know
and on what grounds we can be said to know. Epistemology should not be confused with learning
theory, which is an area of psychology. Nor should epistemology be viewed as merely a descriptive
study of what certain people claim to know. Rather, it is a study of how we can rationally move from our
meagre evidence (just how meagre, relative to our conclusions, will become apparent later) to the
conclusions we believe to be justified. Some of the questions we will examine are:
What precisely are we aware of?
Is all empirical knowledge based on experience? Do people have innate knowledge?
Is the physical world as it seems?
Moral theory
As you will learn in the unit on morality, there is an important difference between what is called
normative ethics and what is called moral theory. Normative ethics is the presenting and defending
of different sets of moral rules. Moral theory is largely an analytic concern with the nature of moral
discourse, whether it is to be understood as referring to empirical properties, nonempirical
properties, or to no properties at all, and a concern with the conceptual analysis of moral discourse.
Some of the questions we will examine are:
What is the standard of right and wrong action?
Is there a standard of right and wrong action?
What is the meaning of “morally wrong” and “morally right?”
What is the relationship between morally wrong acts and punishment?
What does moral discourse refer to, if anything?
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Metaphysics
Broadly stated, metaphysics is a study of the nature of reality, an attempt to answer questions about
whether things do or could exist as they are alleged to, and an analysis of the concepts fundamental to
all fields that make claims about existence. For example, metaphysical theories are put forth as to the
meanings of such terms as substance, causality, quality, relation, mind, God, and so on. Some of the
questions we will examine are:
Do people have immaterial minds?
Do sensible qualities exist in the absence of perceivers?
Do people have free will?
Does God exist?
The point has been emphasized already, but keep in mind that these are questions that cannot be
decided empirically. Chemists do not tell us what “substance” or “cause” mean. Nor could a
physiologist determine by empirical means whether or not people have immaterial minds. These, like
all philosophical questions, are solved, if at all, by debate. These debates may make some use of
empirical data, but this should not be construed as deciding these issues empirically.
A brief introduction to logic
The study of logic often helps students to think critically and clearly. As well it should assist you in
presenting, defending, and evaluating arguments. Logic is one of the oldest and certainly one of the
most useful of academic subjects. Few subjects can lay claim to the multiplicity of applications, both
technical and nontechnical, which logic enjoys. After all, every field of enquiry depends on the
application of sound reasoning for its success, and logic is an attempt to study the latter in a
systematic fashion. Logic also has an obvious application to the attempt of everyone to introduce and
sustain coherency among our beliefs about ourselves and the world in which we live.
Some terminology—arguments, premises, and conclusions
In ordinary language we often use words like ‘valid’, ‘argument’ and ‘fallacy’ that have very specific
and precise meanings in logic. For instance, ‘valid’ is often used as a synonym for ‘true’ or ‘good’;
such as “you make a valid point”. Unfortunately, within a philosophical context, this is an incorrect
use of the word valid that is correctly used to describe arguments, and not statements. It will be
important for you to understand these words correctly before tackling the rest of the course. An
argument is a group of statements, one or more of which (the premises) are claimed to provide
support for, or reasons to believe, the other (the conclusion). So, in effect, an argument is a group of
statements standing in the evidence conferring relation characterized by the support the premises of
the argument provide for its conclusion. Clarification is required at this point to avoid confusion with
the terminology being used. It is important to have a clear conception of the usage of the following
terms: “statements,” “proposition,” “argument,” and “inference.”
A statement is defined as a sentence that can be either true or false. Statements can be asserted or
denied, but not all sentences are statements. Questions, suggestions, and commands, for example,
are not true or false. Questions can be asked, suggestions offered, and commands given, but they
cannot be asserted or denied. The type of sentence which is typically a statement is a declarative
sentence. Declarative sentences can be asserted or denied and, as such, they have a truth value.
Statements also have meaning, or information content. However, this definition is usually reserved
for propositions. That is, the meaning or information content of a statement is a proposition.
Statements, as declarative sentences, express propositions. It is propositions then that are either
true or false. So, propositions can be asserted or denied or supposed (entertained). In other words,
no sentence is a proposition. But some sentences express propositions, where a proposition is a
state of affairs that does or does not obtain in the world. For example, when I hear you say, “Sam is
sad,” your words present to my mind the state of affairs, Sam’s being sad. I may believe in Sam’s
being sad, or in other words that that state of affairs obtains in the world; or disbelieve that it does; or
I might remain in doubt about whether or not it does. In this last case, I entertain the state of affairs,
Sam’s being sad, but I neither accept nor reject that it obtains in the world. While some authors
Introduction to Philosophy PHIL 1200 Unit 1 9
differentiate between these two terms, we will use the terms “statement” and “proposition”
synonymously.
There are two salient points with respect to the distinction between sentences and propositions. First
consider the example:
John disliked Paul.
Paul was disliked by John.
They are two different sentences in virtue of their differing arrangement. Yet both sentences express
the same proposition. That is, both sentences suggest the same possible state of affairs. So, when
we believe, disbelieve, or merely entertain that the proposition “John dislikes Paul” obtains in the
world, we are making the same claim for “Paul was disliked by John.”
Second, a sentence is a sentence of a particular language, whereas a statement is not peculiar to
any language. Consider the three sentences:
It is snowing.
Es schneit.
Il neige.
They are certainly different, as they are in three different languages: English, German, and French.
However, they all express the same proposition. That is, they all suggest that the same possible
state of affairs obtains in the world. Appropriately, we can then choose to believe, not to believe or to
simply entertain the possible state of affairs “It is snowing.”
Recall that an argument is a group of statements, one or more of which (the premises) are claimed
to provide support for, or reasons to believe, the other (the conclusion). Premises are statements
providing evidence for the truth of other statements; conclusions are statements for which other
statements provide evidence. Statements standing alone are not premises, nor are they conclusions,
and some groups of statements, for example, a mere list, are not arguments. Being a premise is a
relational status a statement acquires when one claims it provides evidence for another statement’s
truth; being a conclusion is a relational status a statement acquires when other statements provide
evidence for its truth. Being an argument is a relational status a group of statements acquire when
one statement in the group is a conclusion and the others are premises.
Many authors use the term “inference” interchangeably with “argument.” Be careful of this synonymy.
Properly an inference is a reasoning process whereas an argument is a set of statements, or
propositions, standing in an evidence conferring relation. As with “propositions” and “statements,”
this is a very weak identification. In both cases you should understand why the two sets of terms are
not precisely synonymous.
Logic will be concerned with these propositions, or statements, and the relations between them.
Recognizing arguments
In ordinary language, what we call “arguments” often involve much shouting and little persuasion. In
philosophy we hope for the opposite. The ability to recognize arguments is very important because, as
you probably already realize, not all sets of sentences express arguments, and in ordinary language
usage the intention of the speaker is not always straightforward. Generally, a passage contains an
argument if it purports to prove something; if it does not do so, it does not contain an argument.
There are two general conditions that must be fulfilled for a passage to purport to prove something.
First, at least one of the statements must claim to present evidence or reasons (factual claim).
Second, there must be a claim that the alleged evidence or reasons supports or implies something
(inferential claim).
There are numerous examples of non-argument forms such as passages lacking an inferential
claim, conditional statements, and explanations. Sometimes it is particularly difficult to distinguish an
argument from an explanation. The simplest way to understand the difference is to consider the
status of the conclusion. For example, consider the assertion “p because q.” Now, if all parties
concerned agree that q is true, then the assertion is an explanation. However, if the truth of q is a
contentious matter, then “p because q” is an argument. It is certainly interesting to know the different
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non-argument forms but the important skill is to be able to distinguish non-argument forms from
argument forms.
Deduction and induction
The distinction between deductive and inductive arguments is most important for the study of logic. You
should endeavour to ensure you understand the distinction thoroughly. A deductive argument is an
argument in which the premises are claimed to provide necessary support for the conclusion. In other
words, the premises are claimed to support the conclusion in such a way that if they are assumed true,
it is impossible for the conclusion to be false. On the other hand, an inductive argument is an argument
in which the premises do not provide necessary support for the conclusion. The premises only
“probability” support the conclusion. That is, the premises are claimed to support the conclusion in such
a way that if they are assumed true, then the conclusion is unlikely to be false and is probably true.
The salient point of the distinction between inductive and deductive arguments lies in the strength of
the respective argument’s inferential claims.
Validity, truth, soundness, strength, cogency
In further analyzing inductive and deductive arguments, the notions of truth, validity, soundness,
strength, and cogency play a central role by providing further categorization and classification of
inductive and deductive arguments. These terms are introduced to assist you to discriminate good
from bad arguments. You may have used many of these terms synonymously in day-to-day living,
but you will find that in the field of logic, they have distinct and specific meanings.
Arguments, either deductive or inductive, are neither true or false. Only statements or propositions
can be true or false.
Deductive arguments can be valid or invalid. A valid deductive argument is an argument in which the
premises support the conclusion in such a way that, if they are assumed true, it is impossible for the
conclusion to be false. This is because the conclusion of a deductive argument never includes
information not included in the premises. All valid deductive arguments are iron-clad, and
unsurprising. An invalid deductive argument is a deductive argument such that, if the premises are
assumed true, it is possible for the conclusion to be false.
An argument is either valid or invalid only on the basis of the logical relationship between the
premise and the conclusion, regardless of the content of the argument. In the following examples,
surprisingly, the first is valid, and the second is invalid.
Ex #1. All fish are doctors
All doctors are martians
Therefore all fish are martians.
Ex #2 All salmon are fish
All Cod are fish
All Salmon are cod.
Since validity and invalidity has nothing to do with the content of the argument, philosophers use the
concept of “sound” to describe arguments where the premises are true. A sound argument is a
deductive argument that is valid and has, in fact, true premises. Since an argument must be valid to
be sound, only deductive arguments can ever be sound.
The classifications “valid” and “invalid” are not used to describe inductive arguments. The premises of
an inductive argument provide only probable support for the conclusion. This is because the conclusions
of arguments include information not included in the premises; such as, the inference that all penguins
probably have webbed feet, based on the observations of relatively few penguins. Thus, it could never
be the case that the premises of an inductive argument could be said to support the conclusion in such
a way that, if the premises are assumed true, it is impossible for the conclusion to
Introduction to Philosophy PHIL 1200 Unit 1 11
be false. Inductive arguments are either strong or weak. Strength and weakness, unlike validity and
invalidity, generally admits of degrees. For example, consider the following two arguments:
1. 95 percent of all Albertans are rich.
Sally is an Albertan.
Therefore, Sally is rich.
2. 10 percent of all Albertans are rich.
Sally is an Albertan.
Therefore, Sally is rich.
Argument #1 is a strong inductive argument, whereas argument #2 is a weak inductive argument. A
strong inductive argument is an inductive argument such that, if the premises are assumed true, based
on that assumption, it is probable that the conclusion is true. A weak inductive argument is an inductive
argument such that, if the premises are assumed true, then based on that assumption, it is not
probable that the conclusion is true. A cogent argument is an inductive argument that is strong and
has, in fact, all true premises, and if either of these conditions are missing the argument is in cogent.
Good arguments versus fallacies
The last logic term you should know is ‘fallacy’. In common language we often use this word as a
synonym for “mistake” or “false”. In philosophy, we more precisely use ‘fallacy’ to refer to those
mistakes in reasoning that are worth studying because of their regular use and seductive nature.
The best way to think of fallacies is to consider three basic requirements for a good argument:
The premises must be:
1. Relevant to the conclusion.
2. Sufficient to warrant accepting the conclusion.
(The highest grade of logical sufficiency is attained in an argument that is deductively valid, for
then the conclusion cannot possibly be false, provided the premises are true. Frequently,
however, we must rely upon arguments that are not deductively valid, but have a reasonable
degree of inductive strength.)
3. Acceptable in their own right.
(The highest grade of logical acceptability is to have premises known with certainty to be true. But it
is reasonable to accept premises for which we have sufficient evidence to render them probable.)
A premise that is not acceptable, because we lack evidence for it, may of course turn out to be true.
Three basic fallacies or families of fallacies (corresponding to the three requirements on the previous
page):
1. When the requirement of relevance is not met, we have the fallacy of Irrelevant Reason, or non
sequitur.
Example: It has often been noted that the stated reasons for the US invasion of Iraq, to thwart
the use of weapons of mass destruction, has turned out to be moot, as no weapons of this
nature were found in Iraq. Donald Rumsfeld, Secretary of Defense, when asked whether he had
lied to the American people about this replied: “why do you think that the men and women in
uniform every day, when they came out of Kuwait and went into Iraq, put on chemical weapon
protective suits? Because they liked the style?”
2. When the requirement of logical sufficiency is not met, the argument commits the fallacy known
as Hasty Conclusion.
Example: Letter to Ann Landers:
My 16-year-old cousin sent for your booklet called “Teenage Sex and Ten Ways to Cool it” …
When the booklet arrived, she read it right away…Well, Ann Landers, three months later she
was pregnant and got married very fast. …What I want to know is why do you recommend
booklets if they don’t do any good?
Highly Disappointed
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3. When one or more of the premises fail to meet the requirement of logical acceptability, the
fallacy of Problematic Premise is committed.
Example: In the late 1960s, just after the release of the Beatles’ album Abbey Road, many
people argued:
Paul McCartney is dead
• There will be no more Beatles albums.
Their belief that McCartney was dead was based upon “clues” on the covers of several Beatles
albums, and maintained despite overwhelming evidence that McCartney was, in fact, still alive.
The following table summarizes this discussion of logical terms:
Word Means Can be
Statement The basic unit of logic. True or false
Argument 2 or more statements such than one or more
supports another.
Deductive or Inductive
Deductive
argument
An argument where the scope of the premises is
limited to the scope of the conclusion.
Valid or Invalid
Inductive
argument
An argument where the scope of the premises
goes beyond the scope of the conclusion
Strong or Weak
Sound An argument that is valid and has all true
premises
Very persuasive.
Fallacy An argument commonly accepted as good
reasoning despite being defective reasoning.
Seductively persuasive & often very
expensive.
Argument forms: Proving invalidity
A key point in understanding deductive arguments is to understand how validity is discerned by the
form of the argument. Proving an argument to be deductively valid is often a long and challenging
process. On the other hand, proving invalidity is sometimes much easier.
An important, and in some sense intuitive, method of proving invalidity is the counterexample
method. As you work through this section, recall that a valid argument is a deductive argument
where the conclusion must be true if the premises are true. Thus, an argument that can have true
premises and a false conclusion is invalid.
You should also remember that validity is exclusively a matter of the structure of the argument, not
the content. Any argument that has the same structure as a invalid argument is also invalid,
regardless of the truth of its premises.
Consider the following argument form,
All A are B.
All C are B.
Therefore, all A are C
This example effectively introduces the important “substitution instances” definition of invalidity: An
argument is invalid if and only if its form allows for a substitution instance having true premises and a
false conclusion.
Considering the above example, let:
A = Men, B = Mortal, and C = Cats.
Applying this substitution we get,
All men are mortal.
All cats are mortal.
Therefore, all men are cats.
Introduction to Philosophy PHIL 1200 Unit 1 13
This is a clear example of an argument in which all the premises are true and the conclusion is false.
This shows that the form of the argument is invalid
Basic valid argument forms
Propositional logic is a branch of deductive logic developed by the Stoic school of philosophers, who
flourished in Athens in the third century B.C.E., beginning about 20 years after the death of Aristotle.
The Stoic school is named after the “Painted Porch” (stoa poikile), a landmark close to their meeting
place. The Stoics’ contribution to logic was underrated in the period 200 B.C.E.-1879 C.E, which is a
long time to wait for anyone to wait for respect.
In representing these argument forms, we commonly use variables or dummy letters to stand for
COMPLETE statements or propositions—capable of being true or false when standing alone—not
only for class terms as in the Aristotelian SCS.
Here are some technical terms used in the Stoics’ propositional logic:
• A compound statement of the form ‘A and B’ (where ‘A’ and ‘B’ are both complete statements in
their own right) is called a conjunction or a conjunctive statement. Each of the simpler
statements which are parts of the conjunction is called a conjunct.
• A compound statement in the form ‘Either A or B’ is called a disjunction or a disjunctive
statement. Each of its subparts is called a disjunct.
• A disjunction may be inclusive or exclusive. It is called inclusive when it is intended to mean
“Either A or B is the case, and I’m not ruling out the possibility that both A and B are the case.” If
the intended meaning is “Either A or B, but definitely not both,” that is an exclusive disjunction.
“Either … or” in English has this regrettable ambiguity.
A compound statement of the form “If A, then B” is called a hypothetical statement or a
conditional statement. In a conditional statement, the “if”-clause (A) is called the antecedent,
and the “then”-clause (B) is called the consequent.
Here are some basic valid argument forms you will need to know. They are commonly known by
their Latin names, but we will also refer to them by reference to their structure. For instance, the
first argument form is the disjunctive syllogism, also known as denying the disjunct.
1. Disjunctive Syllogism (a disjunct) (Valid for both the inclusive and the exclusive ‘or’):
Either A or B
Not A
∴ B.
Example: I’ll either Fish or Cut Bait
I hate cutting bait
Therefore I’ll fish.
2. Modus Ponens (Affirming the Antecedent):
If A, then B
A
∴ B.
Example: If I work hard, then I can get a good grade.
I am working hard,
Therefore I will get a good grade.
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3. Modus Tollens (Denying the Consequent):
If A, then B
Not B
∴ Not A.
Example: IF I work hard then I will get a good grade.
I did not get a good grade
Therefore I did not work hard.
4. Hypothetical Syllogism (Hypothetical Chain, Conditional Chain):
If A, then B
If B, then C
∴ If A, then C.
Example: If I study then I can pass the test
If I pass the test then I can complete my degree
Therefore If I study I can complete my degree.
5. Dilemma (Valid only for the inclusive ‘or’):
Either A or B
If A, then X
If B, then Y
∴ Either X or Y.
Example: I must either walk or drive to the store
If I walk, then I will get sore feet.
If I drive, I’ll be burning expensive gas.
Therefore I’ll either have sore feet or burn expensive gas.
6. Affirming a Disjunct (Valid only for the exclusive ‘or’):
Either A or B
A
∴ Not B.
You can get academic credit for either a full term, or half term logic course (but not both).
I have credit for a full term course.
Therefore I will not get credit for a half term course.
Two common, seductive fallacies:
1. Denying the Antecedent:
If A, then B
Not A
∴ Not B.
If I pass the test then I must have studied
I did not pass the test
Therefore I did not study.
2. Affirming the Consequent:
If A, then B
B
∴ A.
If I work hard then I’ll pass the course.
I passed the course,
Therefore I worked hard.
Introduction to Philosophy PHIL 1200 Unit 1 15
The dilemma
One argument form philosophy students should study closely is the dilemma, as it is an extremely
common and powerful argument form. In ordinary English, ‘dilemma’ is often taken to be a
particularly intractable problem. In logic, the dilemma has a particular form which often presents as
a choice between two undesirable alternatives.
Form of the Dilemma:
Either A or B
If A, then X
If B, then Y
∴ Either X or Y.
Example
Either the general deliberately disobeyed his orders, or he failed to understand them. If he disobeyed
his orders, he was disloyal; and if he failed to understand them, he was stupid. Therefore, he was
either disloyal or stupid.
A = The general deliberately disobeyed his orders.
B = The general failed to understand his orders.
X = The general was disloyal.
Y = The general was stupid.
Tactics for answering a dilemma:
1. Going between the horns.
This involves denying the disjunctive premise, ‘Either A or B’. If you had evidence that the
general’s secretary was an enemy spy who changed the orders transmitted to him, you could go
between the horns of the dilemma in this example. If the disjunctive premise has the form ‘Either
A or not A’, then obviously you cannot go between the horns.
2. Grasping one of the horns.
This involves denying one of the conditional premises, ‘If A then X’ and ‘If B then Y’. One could
grasp the first horn of this dilemma by arguing that the general believed the orders came from an
unauthorized person and not from his lawful superiors. The second horn could be grasped by
arguing that the orders were unclear.
3. Charging the bull, or constructing a counter dilemma. (You must, of course, be in a position to do
this without denying something you know to be true.)
For example: Either the general deliberately disobeyed his orders, or he failed to understand
them. If he deliberately disobeyed them, they must have been unlawful; and if he failed to
understand them, they must have been unclear. Therefore, the orders were either unlawful or
unclear.
Reductio ad absurdum, or indirect proof
Another useful argument for is the reducio ad absurdum. Often called ‘reductio’ in ordinary usage.
In logic, nothing can be both true and false at the same time, so that any argument that has the
consequence of something being both true and false simultaneously is absurd.
The Form of a reductio argument is:
To prove Not S:
Assume: S.
Deduce from S either a false statement, or the contradictory of S (i.e., Not S), or a
self-contradictory statement (T and Not T).
Conclude that S must be false; hence Not S is the case.
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The Reductio ad absurdum may be regarded as an extended Modus Tollens:
If S, then (T and Not T)
Not (T and Not T)
∴ Not S.
A mathematical example
A rational number is one that can be expressed as a simple fraction, that is, as the ratio of two
integers (whole numbers). The Greek philosopher and mathematician Pythagoras (sixth century
B.C.E.) is credited with the discovery that there is no rational number whose square equals two—in
other words, that the square root of two is an irrational number. This conclusion is easily proved by
reductio ad absurdum.
Assume that there is some rational number whose square is equal to two. Let this number be
expressed in lowest terms; that is, if the numerator and denominator have a common factor greater
than one, remove it. Thus we have:
2 = (a/b)2 or a2 = 2b2
where a and b have no common factor greater than one. a2 is an even number because it is twice
b2; hence, a is an even number because the square of any odd number is odd. Since a is even, it
can be written as 2c; a2 equals 4c2. Then
4c2 = 2b2 and 2c2 = b2.
It follows that b2 is even, and so is b. We have shown that a and b are both even. This contradicts
the assumption that a/b is a rational number written in lowest terms. Therefore, there is no rational
number whose square equals two.1
In ordinary language, we often use a similar reasoning technique by referring to things that would be
absurd such as “when pigs fly”. This more common form of reductio argument relies on common
agreement as to what is absurd; when significant cultural or philosophical differences occur, it is
easy for a reductio argument to be less then persuasive.
For instance, I might argue that a logical consequence of certain changes to the medicare healthcare
system might be a ‘for profit’ healthcare system. This argument would be a persuasive reductio
argument in Canada, but would probably be much less effective in the USA.
Endnote
1 Wesley C. Salmon, Logic, 3d ed. (Englewood Cliffs, NJ: Prentice-Hall, 1984), p. 33.
Unit summary
In this unit we have provided an overview of philosophy, one that will guide you as you proceed
through this manual, and which you may want to supplement and even to criticize as your
appreciation for philosophy develops. We have also included a brief introduction to logic designed to
provide you with a conceptual framework for tackling some of the difficult theories, problems, and
concepts presented in the following pages. We suggest that you review this unit often; as your
understanding grows along with the units you study, the ideas presented in this introduction will
become clearer to you. This is especially true of the logic material. Many of the units presuppose an
understanding of elementary logic, and so your comprehension will be rewarded by a careful
attention to the logic material. However, you will find that working your way through the units will help
you with the logic material as well. In a sense, the units provide a hands-on training in logic, and so
your understanding of logic no doubt will develop as you make your way through the following
material.
Introduction to Philosophy PHIL 1200 Unit 1 17
Assignment
Look for assignment 1 located in the assignments section. Check the schedule for the due date. Be
sure to submit the honesty declaration when submitting assignment 1.
Glossary
Argument
Contradiction
Deductive
Fallacious argument
Implication
Inductive argument
Inference
Logic
Premise
Rules of inference
Statement
Sound argument
Valid argument
Supplemental readings
Bergmann, M., J. Moore, and J. Nelson. (1980). The Logic Book. New York, NY: Random House. An
advanced book for students wishing to investigate the purely formal features of argument.
Govier, Trudy. (1985). A Practical Study of Argument. Belmont, CA: Wadsworth. A good introduction
to argument that complements the discussion of the fallacies presented in the Logic Primer.
Hollis, Martin. (1985). Invitation to Philosophy. London: Basil Blackwell.
Johnson, R. H., and J. A. Blair. (1983). Logical Self-Defence. Toronto: McGraw-Hill. A nontechnical
guide to the fallacies.
Kahane, Howard. (1980). Logic and Contemporary Rhetoric. Belmont, CA: Wadsworth. An excellent
guide to the fallacies we commit in everyday argument. Numerous illustrations.
Kahane, Howard. (1982). Logic and Philosophy. Belmont, CA: Wadsworth. An introduction to
symbolic logic. Difficult for the novice philosopher but worthwhile if you are interested in
pursuing logical studies.
Taylor, A. E. (1979). Socrates. New York: Doubleday Anchor. A careful and faithful study of the great
philosopher.
