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1. Phil. 201 Introduction To Logic Prof. Tony Roark
Spring 2006
2. On your 3”x5” card: “Official” BSU name
What you’d like to be called
Previous Phil. courses taken
Why are you here?
Interesting fact about yourself
Special concerns or needs
3. Contact Information Email: troark@boisestate.edu
Web: www.boisestate.edu/people/troark
Phone: 426-3378
Hoof: 1910 Lincoln Ave, Rm. 106
ESP: (call your shrink)
4. Our Text Introduction to Logic 8th ed. (custom-bind)
Patrick Hurley
Avail. @ Bookstore
Best thing going ‘til I write my own text.
5. Course Requirements Homework
Quizzes
Exams
6. Homework Exercises from the text.
Posted on the web Mondays.
Due Fridays; bring two copies to class, turn one in as you enter, keep one to “grade”.
Credit for evidence of good-faith effort.
10 assigned, two “freebies.”
40 pts. of 400 total possible.
7. Quizzes 11 given; lowest score dropped.
Given at beginning of class Mondays.
Returned Wednesdays.
Graded for correctness.
100 pts. of 400 total possible.
8. Exams Three of them.
2/17 covers Chs. 1, 4, 5 (75 pts.)
3/24 covers Ch. 6, §7.1, §7.2 (85 pts.)
Final covers §7.3-§7.7 (100 pts.)
260 pts. of 400 possible.
9. Policies All handwritten work must be in pencil; work done in pen receives no credit.
Except in the case of an emergency, no late work will be accepted.
I’m a reasonable person -- communicate!
Don’t cheat.
10. So What Is Logic? “[T]he organized body of knowledge, or science, that evaluates arguments.” (Hurley, p. 1)
The branch of philosophy concerned with the analysis and evaluation of arguments. (ŕ la Roark)
11. So What’s an Argument? A heated exchange or confrontation?
(No.)
A group of statements (at least two), one or more of which (the premises) are alleged to constitute rational grounds for accepting the remaining statement (the conclusion) as true.
12. “Guinness is better than Budweiser.”
An argument?
No.
Why not?
It’s too small (at least two statements required).
13. “In a recent taste test, eight out of ten people preferred Guinness over Budweiser.
“Moreover, Guinness won the ‘Golden Hop Award’ at this year’s brewmaster’s competition, while Budweiser did not.
“Therefore, Guinness is better than Bud.”
An argument?
Yes!
14. “Professor Roark thinks that Guinness is sublime, but he regards Budweiser as being unfit for human consumption.
“Hence, Guinness is better than Bud.”
Argument?
Yes!
15. So What’s a Statement? A declarative sentence (or independent clause) that has a definite truth value (true or false) on some interpretation.
“Interpretation”?
“The sound is very deep.”
16. Statements? “The sum of five and seven is thirteen.”
Statement
“Is eleven a prime number?”
Not a statement
“Don’t listen to that music so loud!”
Not a statement
“God exists.”
Statement
17. Don’t confuse knowledge of truth-value with possession. “George W. Bush had Wheaties for breakfast this morning.”
“The 801st numeral in the decimal expansion of pi is ‘3’.”
18. Some Conclusion Indicators therefore
hence
so
consequently
it follows that
entails
thus
for this reason
necessarily
wherefore
as a result
we may infer
19. Some Premise Indicators since
for
because
as
given that
assuming in that
inasmuch as
owing to
may be inferred from
for the reason that
as indicated by
20. “Since the good, according to Plato, is that which furthers a person’s real interests, it follows that in any given case when the good is known, men will seek it.”
21. “Since the good, according to Plato, is that which furthers a person’s real interests, it follows that in any given case when the good is known, men will seek it.”
Premise: “The good, according to Plato, is that which furthers a person’s real interest.”
Conclusion: “In any given case when the good is known, men will seek it.”
22. Two types of claims made in an argument
A factual claim: the premises are alleged to be true.
An inferential claim: the truth of the premises is alleged to have a logical bearing on the truth of the conclusion.
23. Two important types of non-arguments
I. Conditional statements
II. Explanations
24. I. Conditional Statements Take the form: “If ... , then ... .”
“If ...” clause is called the antecedent.
“then ... “ clause is called the consequent.
“If it rains, (then) I won’t go.”
Antecedent: “It rains.”
Consequent: “I won’t go.”
25.
The relationship between antecedent and consequent should not be thought of as causal or temporal.
Q: How ought one to express the relationship between a car’s having gas in its tank and its running?
26.
“If there’s gas in the tank,
then the car is running.”
But that’s FALSE!
“If the car is running,
then there’s gas in the tank.”
That’s TRUE!
27.
“If there’s gas in the tank,
then the car is running.”
But that’s FALSE!
“If the car is running,
then there’s gas in the tank.”
That’s TRUE!
28. Think of it this way: The antecedent expresses a sufficient condition for the truth of the consequent.
The consequent expresses a necessary condition for the truth of the antecedent.
If [sufficient], then [necessary].
29. Exercise #2, §1.2 VI. Being an animal is a _______________ condition for being a tiger.
Sufficient: If x is an animal, then x is a tiger.
Necessary: If x is a tiger, then x is an animal.
Necessary!
30. Conditional statements are NOT arguments
“If the moon is made of green cheese, then the moon is made of cheese.”
31. But this IS an argument “If the moon is made of green cheese, then it’s made of cheese.
“So, if the moon isn’t made of cheese, it’s not made of green cheese.”
32. And so is this “The moon is made of green cheese.
“So it’s made of cheese.”
33. II. Explanations Answer “why?” questions.
“Why do plants need water to live?”
“Because water (H2O) contains hydrogen, and photosynthesis uses hydrogen and carbon dioxide (CO2) to make glucose (C6H12O6), the ‘food’ from which plants grow new cells.”
34. Terminology Explanandum =df the alleged fact to be explained (in our example, the necessity of water for plant life)
Explanans =df the alleged facts that are claimed to do the explaining (in our example, chemical facts relating to photosynthesis)
35. Explanations are NOT arguments Explanans
Claimed to
shed light on
Explanandum Accepted fact
36. Explanations are NOT arguments Premises Accepted fact
Claimed to
prove
Conclusion
37. Before Friday:
Get a copy of Hurley.
Check out the course website.
Read §§1.1-1.4.
