This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
1 Arguments in Philosophy Introduction to Philosophy
2 Arguments Philosophy is the art of constructing and
evaluating arguments Its all about the argument Arguments are meant
to be convincing So philosophers must be sensitive to what makes an
argument convincing Or not
3 Thinking Critically First step: Think Critically What is the
argument trying to say? Why does the argument succeed, or not?
Whats good, bad, or indifferent? The form of the argument Whats the
point? How do we get to the point? Structure How do the parts of
the argument fit together?
4 General Structure In general, arguments consist of: The
thesis or position argued for The conclusion The reasons why the
conclusion should be accepted The premises Usually this is written
in standard form: Premise 1 (Justification) Premise 2
(Justification) Therefore, Conclusion (Justification)
5 Two kinds of argument In general, there are two kinds of
argument: Deductive Arguments Inductive Arguments These arguments
work (slightly) differently, so theyre evaluated differently
6 But lets be more specific A statement is any unambiguous
declarative sentence about a fact (or non-fact) about the world. It
says that something is (or isnt) the case. An argument is a series
of statements meant to establish a claim. A claim or conclusion is
the statement whose truth an argument is meant to establish. A
statements truth value is either true or false. All statements have
a truth value. A statement is false when what it says about the
world is not actually the case. A statement is true when what it
says about the world is actually the case. A premise is a statement
that is used in an argument to establish a conclusion.
7 Deductive Arguments A deductive argument is: VALID if its
premises necessarily lead to its conclusion. That is, if you were
to accept that the premises are all true, you must accept that the
conclusion is true. SOUND if it is valid and you accept that all
its premises are true. A good, convincing argument is sound. A bad
argument is any other kind of argument. VALIDITY + TRUE PREMISES* =
SOUND *or, at least, accepted premises
8 Examples All people are mortal. Socrates is a person.
Therefore, Socrates is mortal. Sound All people are mortal. My dog
is mortal. Therefore, my dog is a person. Invalid. Oranges are
green. All green things make me sick. Therefore, oranges make me
sick. Valid. Not sound. Whales know how to play hockey. Therefore,
Canadians like winter. Invalid.
9 Notice Validity does not depend on the truth of the premises.
All people are mortal. My dog is mortal. Therefore, my dog is a
person. The premises are true. But the argument is still invalid.
Soundness does not depend on the truth of the conclusion. An
argument can be bad even if the conclusion is obviously true.
10 Evaluating Deductive Arguments Good arguments must be sound.
If you want to accept of an argument, you would have to show both
validity and soundness Bad arguments can be bad in two ways:
Invalid You can show that the conclusion does not follow from the
premises Unsound You can show that at least one premise is
11 Inductive Arguments Inductive arguments are not truth
preserving Even in a good inductive argument where the premises are
true, the conclusion does not have to be true. At most, the
conclusion is most likely true. Inductive arguments are meant to
make conclusions more likely or more acceptable.
12 Inductive Arguments An inductive argument is: STRONG if its
premises make the conclusion probable That is, if you were to
accept the premises as true, then you would have to accept that the
conclusion was probably true COGENT if it is strong and its
premises are accepted A good, convincing argument is cogent.
STRENGTH + TRUE PREMISES* = COGENT
13 Examples This cooler contains 30 cans. 25 cans selected at
random contained soda. Therefore, all the cans probably contain
soda. Cogent This cooler contains 30 cans. 3 cans selected at
random contained soda. Therefore, all the cans probably contain
soda. Weak Every monkey Ive seen (over 500) has blue teeth.
Therefore, the next monkey I see will probably have blue teeth.
Strong, but not cogent
14 Notice Strength admits of degrees. An argument can be
stronger or weaker Usually, the more evidence available, the
stronger the argument Strength does not depend on the truth of the
15 Evaluating Inductive Arguments Good arguments must be
cogent. If you want to accept of an argument, you would have to
show both strength and cogency Bad arguments can be bad in two
ways: Weak You can show that the premises does not make the
conclusion more probable Not cogent You can show that at least one
premise is unacceptable
16 Argument by Analogy One particular kind of inductive
argument is an Argument by Analogy Comparison of two or more things
Concludes that they share characteristic(s) Because they share
other characteristic(s) Example: Watches exhibit order, function,
and design. They were also created by a creator. The universe
exhibits order, function, and design. Therefore, the universe
probably was created by a creator. Evaluated like other inductive
17 In Practice Identify the conclusion What is the claim?
Identify the premises How is the claim supported? Often, we first
have to get rid of anything unnecessary mere rhetorical flourishes,
repetitions, and irrelevancies. Reformulate the argument Try to put
it into standard form Often, well have to add premises that are
implied but not stated.
18 In Practice Identify the form of the argument How are the
premises supposed to lead to the conclusion? Deductive? Inductive?
Assumptions? Subarguments? (This will help us add/delete premises)
Evaluate the argument Valid? Sound? Strong? Cogent? WHY?
19 Example For Death is to be as it were nothing, and to be
deprived of all sensation... And if no sensation remains, then
death is like a dreamless sleep. In this case, death will be a
blessing. For, if any one compares such a night as this, in which
he so profoundly sleeps as not even to see a dream, with the other
nights and days of his life, and should declare how many he had
passed better and more pleasantly than this night, I think that not
only a private man, but even the great king himself, would find so
small a number that they might be easily counted.
20 Example For Death is to be deprived of all sensation... if
no sensation remains, then death is like a dreamless sleep....death
will be a blessing....if any one compares such a night [of sleep
without dreams]... with the other nights and days of his life, and
should declare how many he had passed better and more pleasantly
than this night, I think.. [he] would find so small a
21 Example Death is to be deprived of all sensation. If no
sensation remains, death is like a dreamless sleep. Anyone will
consider a dreamless sleep better than most days and nights. ---
Death is a blessing.
22 Example Death is to be deprived of all sensation. If no
sensation remains, death is like a dreamless sleep. Death is like a
dreamless sleep. Anyone will consider a dreamless sleep better than
most days and nights. Anyone will consider death better than most
days and nights. Anything that is better than most days and nights
is a blessing. --- Death is a blessing.
23 Example Death is to be deprived of all sensation.
(Assumption) If no sensation remains, death is like a dreamless
sleep. (Assumption) Death is like a dreamless sleep. (Conclusion
from 1 and 2) Anyone will consider a dreamless sleep better than
most days and nights. (Assumption) Anyone will consider death
better than most days and nights. (Conclusion from 3 and 4)
Anything that is better than most days and nights is a blessing.
(Assumption) --- Death is a blessing. (From 3, 5, and 6)