1. The Philosopher’s Toolkit Write as a thinker, think as a writer.

2. Basic Tools for Argument 1.1  Nit-picking through  Arguments  Premises  Conclusions

3. Argument: precise reasoning  An inference from one or more starting points (premises) leading to an end point (conclusion).  Arguments show that something is true.  Arguments are rational.

4. Premises and Conclusions  Premises make truth claims that imply conclusions.  All men are mortal (1 st premise)  Socrates is a man (2 nd premise)  Socrates is a mortal (conclusion)  If the premises are true, then it follows that the conclusion is true.

5. Grounds for Premises  Premises may be settled (basic) conclusions to a solid argument.  “I think, therefore I am.”  Premises may need no further justification.  “All bachelors are unmarried.”

6. Basic Tools for Argument 1.2  Deduction  True premises guarantee the certainty of the conclusion.  The murder of King Hamlet was planned.  Claudius had the most to gain by killing King Hamlet.  Claudius killed King Hamlet.

7. 1.2 Deduction: ambiguous premises  My late husband Laius was killed at a crossroads in a right-of-way dispute.  My new husband Oedipus killed a man once at a crossroads in a right-of-way dispute.  Oops!  We must not jump to conclusions because the premises may seem true.

8. Basic Tools for Argument 1.3  Induction  Premises make the conclusion necessary and with probable certainty.  Below: induction or deduction?  The sun always rises.  The sun rose today.  The sun will always rise.

9. Misleading Similarities  Below is an induction:  Some elephants like chocolate.  This is an elephant.  This elephant likes chocolate.  Below is a deduction:  All elephants like chocolate.  This is an elephant.  This elephant likes chocolate.

10. 1.3 Induction: Nature’s Uniformity  If nature’s laws are observed as uniform, then the past is a reliable predictor of the unobserved future.  However, we must admit to a limited knowledge of the observed uniformity of nature.

11. Basic Tools for Argument 1.4  Validity: what creates conviction.  Everyone at Wuthering Heights is a block of cheddar.  Heathcliff lives at Wuthering Heights.  Heathcliff is a block of cheddar.  The above argument is valid, but not true. Validity is content-blind. A ridiculous argument can be valid.

12. 1.4 Continued…Sausage  The Truth Machine  Deductive arguments are best because they demand good ingredients (true premises).  These create sound arguments.  But sound arguments rest on validity or invalidity.

13. Invalid Arguments: Unsound  Put in false premises  Get out true or false conclusion.  Put in true premises  Get out true or false conclusion.

14. Valid Arguments: Sound  Put in false premises  Get out true or false conclusion.  Put in true premises.  Get out only true conclusion.

15. Soundness  When a valid argument and true premises are combined and lead to a true conclusion we have a sound argument.  We must accept a sound argument.  All sound arguments must be valid.

16. In Reasoning We Must…  Attack the premises from which someone reasons.  Show that the argument is invalid, whether or not the premises are true.

17. 1.5 Invalidity  If premises of an invalid argument are true, the conclusion may be false.  Vegans do not eat sausages.  Gandhi did not eat sausages.  Therefore, Gandhi was a vegan. All three propositions are true, but...

18. It is invalid to say that, because  All cats are carnivores.  President Bush is a carnivore.  Therefore President Bush is a cat.  True premises/false conclusion

19. Therefore, Invalidity is…  Not settled by truthfulness of premises.  But by logical relations among them.

20. Thus, good thought and writing  Make truthful claims that are grounded in good arguments.  Gain veracity or weight by showing how the truth claim comes about.

21. 1.6 Consistency  The cornerstone of rationality.  The property of two or more statements.  Apparent or real.  Murder is wrong.  Abortion is not murder.  Abortion is not wrong.

22. Consistency continued  Exceptions to Rule?  It is raining and it is not.  My home is not my home.  Paradox  Jesus was God and a man.  Philosophy  God is good.  God allows evil to occur.

23. 1.7 Fallacies  Instances of poor reasoning.  Faulty inference.  All invalid arguments are fallacious.  Not all fallacies are invalid arguments.

24. Formal Fallacies: faulty form.  If Mr. B won the lottery, he’ll be driving a yellow Mini today.  Mr. B is driving a yellow Mini today.  Mr. B won the lottery!

25. Informal Fallacies: faulty content  If I’ve tossed seven heads in a row with my coin, I am due to toss tails for # 8.  I’ve tossed seven heads.  I will probably toss a tail this time.  No: the odds are always 50:50.  The first premise is false.

26. 1.8 Refutation & Tools  To show that an argument is wrong, you must demonstrate  That the argument is invalid.  Conclusion does not follow from premises.  That one or more premises is false.  That the conclusion must be false.

27. Refutation: Inadequate Justification  Dubious Premise:  There is intelligent life elsewhere in the universe.  There can be no adequate justification for this claim, so it is dubious (doubtful), and we may ignore it.

28. Refutation: Conceptual Problems  Vague concepts used as precise concepts lead to distortion.  Argument  Government is only obliged to provide assistance to those who do not have enough to live on. How much is that? Please define this vague concept. The use of vague concepts in precise arguments we end up with distortions.

29. Axioms & Indeterminacy  Initial claims that need no justification.  No rational person could deny them.  Premises true by definition (obvious)  Primitive sentences (lines/points)  Universal? (unalienable)

30. Definitions I  Agreement on terms necessary.  Clear conclusions more likely.  Problems leading to confusion:  Too narrow  Too broad  Rules of thumb necessary  Problem of language

31. Certainty and Probability  Rene Descartes’ Method of Doubt  “I think, therefore I am” cannot be doubted.  Everything else must be doubted unless it is clear and distinct.  It is possible to arrive at certainty, but only by doubting everything first.

32. Certainty and Probability 2  Ludwig Wittgenstein: (1899-1951)  It makes no sense to doubt certain things.  We can figure things out with certain degrees of probability.  Caveat: we must give thought to our concepts.

33. What is Certainty?  A feeling or mental state where the mind believes X without doubt.  A mental admission of the necessarily true or false.

34. The Problem of Skepticism  Absolute certainty may not be attainable in any or all cases.  Probability is our only recourse to skepticism.  Objective Probability: radioactive decay  Subjective Probability: coin flipping

35. Certainty and Validity  In a sound deductive argument, the conclusion must follow with certainty, but must also be true.  All humans are mortal.  Socrates was a human.  Therefore, Socrates is a mortal.

36. Tautologies, self-contradictions, and the law of non-contradiction  Tautology: a sentence that is necessarily true.  P or Not-P  “Today is Xday.”  “Atoms are invisible.”  “Monkeys make great lasgna.”  All valid arguments are tautologies.

37. Tautologies, self-contradictions, and the law of non-contradiction  Law of non-contradiction is a tautology.  Not (P and Not-P)  Whether P is true or false, the statement is true.  Attempts to break the law of non-contradiction are themselves contradictions and are therefore always wrong. One cannot claim that something is true and not true at the same time. “What is is and cannot not be.” (Parmenides) “It is what it is what it is.” (Scott)