Transcript What is Logical Form?

Philosophy 1010
Class #2
Title:
Instructor:
E-mail Address:
Introduction to Philosophy
Paul Dickey
[email protected]
Reading Assignment for next week:
Logic Appendix 1.8 (Text, 9th edition. Please see
class website -- www.quia.com.)
Complete the logic Homework Assignment also
found on the site.
The Father of Western Philosophy
•
Socrates, 460-399 B. C.
•
Socrates' deserves credit for rigorous, ethical
investigation. His conversations with his fellow
Athenians are the first records we have of an
individual, by careful reasoning, trying to discover
the guiding principles of moral choices.
•
But be careful. There were many Greek thinkers
(actually known as “The Pre-Socratics”) prior to
Socrates who developed profound insights into the
nature of the universe and man’s place in it.
•
Socrates built a reputation on questioning
conventional beliefs, thus embodying the
nature of philosophy itself.
What is the Socratic method?
•
“Teaching by Asking Instead of by Telling”
•
Socrates engaged himself in questioning students in
an unending search for truth. He sought to get to the
foundations of his students' and colleagues' views by
asking continual questions until a contradiction was
exposed, thus proving the fallacy of the initial
assumption.
•
This became known as the Socratic Method, and may
be Socrates' most enduring contribution to philosophy.
•
Socrates was both a real philosopher and the major
character in Plato’s (his student’s) dialogues. Thus, it
is not clear to what degree Socrates was a precursor
to Plato’s ideas or was a mouthpiece for Plato to put
forward his own views.
Video
Plato’s Dialogues &
the Socratic Method
•
Plato’s dialogues demonstrate the Socratic Method.
•
In The Euthyphro, Plato shows Socrates questioning
traditional religious beliefs and the nature of religious
duty. He asks “what is it to be holy” and Euthyphro
says that being holy is “doing what the gods love.”
•
Class, has Euthyphro given a good answer to the
question? Does he really understand or is he just
assuming that he knows?
•
Socrates probes further: what makes a thing holy? Is
an act holy because it is loved by the gods or do the
gods love what is holy because it is holy?
•
If the first, are the gods capricious and random and
be able to select anything to be holy? If the latter,
then we have not answer the original question at all.
Plato’s Dialogues &
the Socratic Method
•
In Plato’s The Republic, Socrates questions
Thrasymachus who states that justice is whatever is
to the advantage of the strong, that “might makes
right.”
•
Socrates asks what if the powerful pass laws that in
error do not benefit themselves. Would not justice
then be following laws that do not benefit the
strong? Then justice would be in following laws that
do not benefit them.
•
Thus, Socrates has pointed out to Thrasymachus
that his commonly held view is quite likely
inconsistent, or at least needs to be qualified and
made clearer.
Plato’s Dialogues &
the Socratic Search for How to Live
•
Plato’s dialogues demonstrate that Socrates was
not just trying to be “smart” but was in the profound
pursuit of how one should live.
•
In The Apology, Socrates defends his way of life.
He proclaims that his mission came from a divine
commandment to seek wisdom. Thus, he
questioned everyone he professed knowledge to
find wisdom, only to find that the wisest man is he
who knows he does not know.
•
Even in the face of death, Socrates proclaims he
can act no differently. It is better to obey the
gods than man. The unexamined life is not worth
living. His pursuit of philosophy is following the
instruction of the gods.
Video
Plato’s Dialogues &
the Socratic Search for How to Live
•
In the Crito, Socrates is awaiting execution in his
prison. Crito suggests that for the benefit of his
friends and family, Socrates should escape. “It is
the opinion of all of your friends, Socrates.”
•
Socrates replies that in order to act on reason
alone, Socrates asks Crito what is right and wrong
and we must not follow the “morality of the many”
but follow what is truly right.
•
Socrates further argues that what is the right way
to live consists in obeying the state in which we
have contracted to live. Thus, we must obey the
laws of the society in which we live, even when
those laws and actions are unjust.
Plato
c. 427-347 B. C.
Plato is history's first great philosopher
because, among other reasons, he provided
the first set of answers to some of the largest
and most difficult questions: What is the
structure of reality? What can be known for
certain? What is moral virtue? What is the
nature of the ideal state?
No philosopher before Plato had ever
attempted such a wide and deep exploration
of philosophical problems.
Plato & the Allegory
of the Cave
•
Plato was a student of Socrates. To better understand
what philosophy is, he describes the nature of
philosophy in the Allegory of the Cave.
•
Plato compares the state of man’s ignorance to living
at the bottom of an underground cave chained so that
such men cannot move. All they see are shadows
created by a fire behind them.
•
Through this symbolism, he then describes the act of
philosophy which he likens to the prisoners being
freed from their chains.
•
Plato is suggesting to us that this process is the
“ascent of the mind into the domain of true
knowledge.” Plato suggests that the aim of
philosophy is freedom from unwarranted belief.
The Allegory of the Cave
Video
The Matrix / The Allegory of the Cave
The Matrix Trailer
Video
The Allegory of the Cave:
The Metal Version
Video
Content begins at 10:30
Ten Minute Break!
What Is
Philosophy?
Disk 1 from “The Examined Life”
Video Series
What Are the Major Fields of
Philosophy?
1. Metaphysics is “the study of reality
or existence.”
Does God Exist?
Does man have a soul? If so, is it
immortal?
Are humans free to choose for
themselves, or are all human acts
determined?
Monism
Monism is the view that all of reality is one kind of thing. If,
for example, you believe that all of reality is matter, or that
God is the only reality, then you are a monist.
The first philosophers (Pre-Socratics) like Thales (c. 600
BCE) Pythagoras (c. 550 BCE) and Heraclitus (c. 500 BCE),
were monists.
Thales' belief that "All is Water" is considered the first
philosophical statement because it explains reality, "All", in
non-religious terms. Every previous description of all of
existence relied upon stories rooted in religious traditions.
Typically, most monists are materialists. In other words,
they believe that the single unifying feature of reality is
matter. Holding this view, materialistic monists argue that
there is no God, Heaven, Hell, soul, or any other "spiritual"
part of reality.
Dualism
Dualism is the view that all of reality is divided into two
kinds of things. Thus, if you believe that all of reality is
divided between the realm of God and the physical
universe, or that there is a "higher world" and a "lower
world", or that reality is composed of spirit and matter,
you are a dualist.
In general, most Christians are dualists. They hold that
reality is divided into two parts. Our souls are eternal
and non-material; our bodies, like the physical universe,
are temporal and material.
Plato's view of reality is often termed dualistic, that is,
he saw reality "dual", divided into two parts. The higher
part of reality consisted of perfect and eternal truths
which he called Forms. Plato held that all physical
things are imperfect copies of Forms. Thus, all physical
triangles are imperfect copies of the Form of Triangle.
What Are the Major Fields of
Philosophy?
WARNING! WARNING! WARNING!
(or rather, in contrast to other areas of study
such as biology where biology studies a
particular domain, Philosophy does not
necessarily have agreed upon assumptions that
it can rely on to define any domain of study.
Thus, metaphysics is more accurately “a
collection of questions that seem to group
together about what is real and what reality is
like.”
NOTE: Biology is the study of life or living matter in all its
forms and phenomena. To do biology, scientists thus must
work with an agreed upon view of what is life.
What Are the Major Fields of
Philosophy?
2. Epistemology is “the study of knowledge.”
(or rather….)
What is the structure, reliability and kinds of
knowledge we have?
What is the meaning of truth?
Is scientific knowledge different than other forms
of knowledge?
Is the nature of knowledge different based on
gender?
In general, philosophers have
explained knowledge in two ways.
 Empiricists argue that all
knowledge begins with the senses.
 Rationalists argue that is
possible for the mind,
independently of the senses, to
gain knowledge.
If you believe that everything you know can be traced back
to information that you saw, heard, touched, smelled or
tasted, then you are an empiricist.
If you believe that you have knowledge of God, heaven, hell,
spiritual aspects of reality, or anything else that didn't come
to you through your senses, then you are a rationalist.
Some rationalists like Plato (427-348 BCE) hold that we are
born with knowledge; other rationalists like St. Augustine
(354-430) believe that God, during our lives, makes it
possible for our minds to know truths that could not be
gained through our senses.
If you don't know for certain that the material world exists, or
that the principles of science qualify as genuine knowledge
or that God exists (or doesn't exist) then, on each of those
issues, you are a skeptic.
What Are the Major Fields of
Philosophy?
3. Ethics is “the study of values and morality
and how they relate to conduct.” (or
rather….)
What is the nature of man’s obligation to other men?
How should we live to be good?
What responsibilities do governments have to their
citizens?
Is man essentially selfish? Or can he be motivated
by principles beyond his own self-interest?
Ethics comes from the Greek word ethos for character. Ethics
is the study of the nature of morality and immorality, of how
humans should, and should not, act. A central ethical
question is, what is the source of moral values?
Here are three of several possible answers:
1. Moral values come from
God. If you hold this position,
then odds are that you believe
that genuine moral values are
unchanging and universal.
What is right, has always been
right; what is wrong, has always
been wrong. God's laws apply to
everyone, in all cultures. This
position would make you a
moral absolutist.
2.
Moral values come from societies. If
you hold this view, then you probably
believe that moral values can
legitimately vary from culture to culture.
Each society can have its own
standards of ethical behavior. What is
right for the Chinese, may be wrong for
Brazilians, and vice versa. This position
would make you a moral relativist.
3.
Moral values are determined by the
utility or usefulness of an action to
promote everyone’s best interest. If
you hold this view, then you are a
utilitarian. Utilitarianism was argued
by John Stuart Mill (1806-1873).
Ten Minute Break!
Logic and Critical Thinking:
An Overview
The background of philosophical and
all rational discussion.
The Fundamental Principle of Critical
Thinking is The Nature of an Argument
•
Making a claim is stating a belief or opinion
-- the conclusion
•
An argument is presented when you give a
reason or reasons that the claim is true. -the premise(s)
•
Thus, an argument consists of two parts,
and one part (the premise or premises)
is/are the reason(s) for thinking that the
conclusion is true.
Two Kinds of Good Arguments
•
A good deductive argument is one in which if
the premises are true, then the conclusion
necessarily (I.e. has to be) true.
•
Such an argument is called “valid” and
“proves” the conclusion.
•
For example – Lebron James lives in the United
States because he lives in Nebraska.
All men are mortal.
Socrates is a man.
____
Socrates is mortal.
•
A sound argument is a valid, deductive
argument in which the premises are in fact true.
Two Kinds of Good Arguments
•
A good inductive argument is one in
which if the premises are true, then the
conclusion is probably true, but not
always. The truth of the premises do not
guarantee the truth of the conclusion.
•
Such an argument is called “strong”
and supports the conclusion.
•
For example: Dan lives in Nebraska
and he loves football, so he is a
Nebraska Cornhusker fan.
•
“Strong” inductive arguments still
can be made “stronger” or “weaker”
by adding or removing premises.
What is “Beyond a Reasonable Doubt” vs “Proof?
•
PROOF requires a valid deductive
argument.
•
“Beyond a reasonable doubt” requires a
level of evidence in an inductive
argument such that if someone were to
believe it were not true, they might still
possibly be right, but that probability is
so remote that reasonable, critical
thinking, people will be satisfied to act
and claim to know without a proof.
How Do Premises Support Conclusions?
For an Deductive argument, premises prove or
demonstrate a conclusion based on if the premises
make the conclusion certainly true.
Consider the argument:
(P1) If it’s raining outside, the grass near the
house gets wet.
(P2) It’s raining outside.
_________________________
The grass near the house is wet.
In a Deductive argument, premises prove a conclusion
based on the logical form of the statement or based on
definitions. It would be a contradiction to suggest that
the conclusion is false but the premises are true.
What is Logical Form?
Consider the following argument:
A good God cannot exist. There is evil in the world and
any God who is good would not permit evil to exist.
This argument can be stated as follows:
(Premise 1) There is evil in the world.
(P2) A God who is good would not permit
evil to exist.
____
(Conclusion) A God who is good does not
exist.
What is Logical Form?
Note that we can symbolize this argument with
variables. In this case, say for example, this
argument could be represented as:
G = A good God exists, E= There is no evil in the
world.
This argument is of the form:
If G  E
~ E (i.e. NOT E or “E is false”)
_____
~G
(NOT G or “G is false”
Thus, it is a valid deductive argument. This is
the deductive rule of Modus Tollens. EVERY
argument that can be represented in this form
is valid, regardless what G and E represent.
How Do Premises Support Conclusions?
For an Inductive argument, premises support
(never prove) a conclusion based on how strongly
the premises provide evidence for the conclusion.
Consider the argument:
(P1) If it’s raining outside, the grass near the house
gets wet when the wind is not blowing strongly
from the North (which doesn’t often occur).
(P2) It’s raining outside.
_________________________
The grass near the house is wet.
How Do We Evaluate an Argument?
There are generally two requirements (and only
two) logically to evaluate a claim –
1) Do the premises support or prove
the conclusion? Or is the argument valid
(if deductive) or strong (if inductive)?
2) Are the premises true?
-- It would be nonsense for you to object
with, for example, “I don’t want to believe
that” or “You shouldn’t say that”, or “Where
did you come up with that?” “That’s not
what my girl friend says,” etc, etc.
Writing Assignment
Worth 5 points in Participation Category.
In response to what we have discussed
tonight, pose a different philosophical
question than you did last week. Rather
than trying to answer the question though,
list and discuss what other relevant
questions might need to be answered or at
least clarified in order that you may even
have a chance to answer this one. Does
your question now seem to you to be a
metaphysical, ethical, or an epistemological
question? Or maybe some other type? Like
last time, please do not use any sources.
Just use your own reflection.