logic; chapter 1 - slide 1 logic - chap. 1 - arguments lwhat is logic? fthe study of the principles...
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Logic; chapter 1 - slide 1
Logic - chap. 1 - arguments
What is logic? The study of the principles used to
distinguish between good and bad arguments.
Clarifications Logic is not the study of the
reasoning process Logic is not primarily concerned
with establishing the truth or falsity of statements.
Logic; chapter 1 - slide 2
Logic - chap. 1 - arguments
Why are arguments important? A way to resolve disagreements
peacefully Part of the process of finding the
truth For conceptual questions,
arguments may be the principal method of determining truth
Central to our humanness
Logic; chapter 1 - slide 3
Logic - chap. 1 - arguments
The notion of an argument A set of statements of which one or
more are put forward as reasons for accepting another statement as true.
Logic; chapter 1 - slide 4
Logic - chap. 1 - arguments
An example of a simple argument If we interfere with the publication of false
and harmful doctrines, we shall be guilty of suppressing the liberties of others, whereas if we do not interfere with the publication of such doctrines, we run the risk of losing our own liberties. We must interfere or not interfere with the publication of false and harmful doctrines. Hence we must either be guilty of suppressing the liberties of others or else run the risk of losing our own liberties.
Logic; chapter 1 - slide 5
Logic - chap. 1 - arguments
Distinguishing between arguments & non-arguments Examples
Logic; chapter 1 - slide 6
Logic - chap. 1 - arguments
I don’t think it would be a good idea to take the American Revolution course this term, because it conflicts with a course I need for my major, and my schedule would have more balance if I took a science course instead.
Nearly half the homes in the country subscribe to cable TV. Basic cable service usually includes local TV channels, such as the four networks, and one or more channels. For an additional fee, subscribers can also receive movie channels and other specialized programs
Logic; chapter 1 - slide 7
Logic - chap. 1 - arguments
Analyzing arguments 3 steps (1) Identify & distinguish between
premises & conclusion(s) Clues
premises & conclusion may occur in any order
Logic; chapter 1 - slide 8
Logic - chap. 1 - arguments
Example: No coal tar derivatives are nourishing foods, because all artificial dyes are coal tar derivatives, and no artificial dyes are nourishing foods.
look for indicator words don’t let flourishes &
repetitions confuse you
Logic; chapter 1 - slide 9
Logic - chap. 1 - arguments
Example: In the twentieth century, physicalism has flourished. But the after-image is not in physical space. The brain-process is. So the after-image is not a brain-process. (J.J.C. Smart, “Sensations and Brain Processes,” Philosophical Review, April 1959)
Logic; chapter 1 - slide 10
Logic - chap. 1 - arguments
missing Ps & Cs do not make an argument invalid (or weak) Example: Mary attended
the opera; so her lamb must have attended the opera too.
several arguments may be strung together
Logic; chapter 1 - slide 11
Logic - chap. 1 - arguments
Example: (1) And now the great question as to the reason why. (2) Robbery had not been the object of the murder, for (3) nothing was taken. (4) Was it politics, then, or was it a woman? (5) That was the question which confronted me. (6) I was inclined from the first to the latter supposition.
Logic; chapter 1 - slide 12
Logic - chap. 1 - arguments
Example (cont’d): (7) Political assassins are only too glad to do their work and to fly. (8) This murder had, on the contrary, been done most deliberately, and (9) the perpetrator had left his track all over the room, showing that he had been there all the time. (10) It must have been a private wrong, and not a political one, which called for such a methodical revenge.
Logic; chapter 1 - slide 13
Logic - chap. 1 - arguments
(2) Analyze the structure of the argument A strategy
(1) list & number each independent clause
(2) use arrows to indicate the relationship between Ps & Cs
(3) use + to indicate that two premises together entail the conclusion
Logic; chapter 1 - slide 14
Logic - chap. 1 - arguments
(4) use separate arrows to indicate that premises independently support a conclusion
(5) indicate whether several arguments are linked in a series
Logic; chapter 1 - slide 15
Logic - chap. 1 - arguments
Example of portraying the structure of an argument It is rarely economical for
two companies to lay cable in the same area and compete directly. This suggests that cable television is a natural monopoly, and should be regulated by the government.
Logic; chapter 1 - slide 16
Logic - chap. 1 - arguments
Another example (1) I can’t think of anything
more futile than worrying about the past. (2) Did you ever meet anyone who could change the course of past events? (3) Of course not. Past events are entirely outside of human control. (4) Think of all the people who continually worry about their past lives, as if worrying made a difference.
Logic; chapter 1 - slide 17
Logic - chap. 1 - arguments
Example (cont’d): (5) I’m sure that if these people would devote as much time and energy to present opportunities as they spend mulling over the past, they would be far better off. (6) I repeat, it’s futile to worry about the past, (7) because the past is something that can’t be controlled.
Logic; chapter 1 - slide 18
Logic - chap. 1 - arguments
(3) Determine whether the argument is deductive or inductive A traditional way of distinguishing
Deductive general to specific
Inductive specific to general The weakness of this way of
distinguishing between deduction & induction
Logic; chapter 1 - slide 19
Logic - chap. 1 - arguments
An alternative and better way of distinguishing between deduction & induction Induction an argument in
which the conclusion goes beyond the premises and accordingly the relationship between the premises & conclusion is one of probability conclusions go beyond, make
a leap into the unknown
Logic; chapter 1 - slide 20
Logic - chap. 1 - arguments
Deduction an argument in which the conclusion is implicitly contained within the premises and which, accordingly, has a relationship of necessity between the premises & conclusion
The function of deductive arguments to clarify, to make explicit
The function of inductive arguments to lead to new knowledge
Logic; chapter 1 - slide 21
Logic - chap. 1 - arguments
Which of these two types of arguments is better? the tradeoff rigor,
precision, guarantee that the conclusion is true if the premises are true vs new knowledge, discovery, prediction
Logic; chapter 1 - slide 22
Logic - chap. 1 - arguments
Clues for distinguishing between inductive & deductive arguments Look at the kind of claim being
made Deductive arguments often,
not always, move from general to specific; inductive arguments often, not always, move from specific to general To chapter 2