The Cure for Fallacies of Clarity. Philosophy and Logic Unit 3, Section 3.4

Transcription

1 he Cure for allacies of Clarity Philosophy and Logic Unit 3, Section 3.4

2 allacies of Clarity: A Diagnosis All four involve some word, occurring in both premise and conclusion, whose meaning shifts in between. It is ambiguous, and we shift from one sense of the word to another It is vague, and we make tiny steps (shifts in truth conditions) across borderline cases We shift from collective to distributive attribution (or vice versa).

3 Diagnosis, continued All four rely on that shift in meaning. he argument seems persuasive only because the shift in meaning is not noticed. If it is noticed: one or another of the premises becomes implausible, or the inference falls apart.

4 Suggested cure Make the meaning explicit his is the special job performed by definitions wo skills. irst: learn the anatomy of a definition. (Study guide 3, #3) Second, learn how to assess a definition. (Study guide 3, #4)

5 he anatomy of definition wo orms 1. a payment is a wage if and only if wages =df.... the definiendum of a definition =df. the term which is defined. the definiens of a definition =df. the terms which set out the precise meaning of the definiendum.

6 he goal of definition o set out the precise meaning of a term. o precisify : to deal with vagueness in terms. he main technique for avoiding slippery slope fallacies. o disambiguate. he main technique for avoiding equivocation, composition, division. o stipulate a meaning for a technical term.

7 hree meanings of meaning the extension of a term P =df. the class of things of which P is true. the intension of a term P =df. a description, criterion, or test which allows one to determine for any object x whether or not x is P. the connotation of a term P (in a given context) is the emotional attitude or reaction that the speaker intends to communicate by using that particular term.

8 he fundamental requirement In any adequate definition, the definiens and the definiendum must have exactly the same extension. he term defined and the terms doing the defining must be true of exactly the same things. o challenge a definition: try to think of some counterexample.

9 As manifested in the form wages =df. a transfer of cash from one person to another for services rendered a payment is a wage if and only if it is a transfer of cash from one person to another for services rendered he definiendum and the definiens must be true of exactly the same things.

10 orm to the rescue If and only if says two things - a payment is a wage if it is a transfer of cash from one person to another for services rendered W and - a payment is a wage only if it is a transfer of cash from one person to another for services rendered W.

11 Let P = the term to be defined S is a sufficient condition for P if and only if anything which is S is also P. S P. (If S then P) he antecedent of a conditional is a sufficient condition for its consequent. if (alone, without only) marks a sufficient condition

12 Necessary condition N is a necessary condition for P if and only if anything which is P must also be N. P N. (P only if N.) Or, equivalently: If ~N, then ~P. (~N ~P) he consequent of a conditional is a necessary condition for its antecedent. only if marks a necessary condition.

13 Why we have so many variants of the conditional P only if D says: D is a necessary condition for P (P D) (~D ~P) P if D says: D is a sufficient condition for P D P P if and only if D says both. (P D) ((P D ) & (D P) )

14 he requirement, re-stated In any adequate definition, the defining terms should provide both necessary and sufficient conditions for the term defined. P only if D and if D then P P D & D P hat is: P if and only if D P D

15 How to think of counter-examples 1. Does the definition provide a correct sufficient condition? Is it true that if there is a transfer of cash from one person to another for services rendered then it is a wage? hink of a case of which the defining terms are true but the defined term is not. eg something which is a transfer of cash...but is not a wage.

16 Counter-examples, step 2 2. Does the definition provide a correct necessary condition? Is every wage a transfer of cash from one person to another for services rendered? hink of a case to which the defined term applies but the defining terms do not. eg, wages that are not transfers of cash...

17 P = the term to be defined (definiendum) D = the terms doing the defining (definiens) A definition says: P D his is false in two cases: P D P D

18 P D P D

19 P D P D D is not a necessary condition for P

20 P D P D D is not a necessary condition for P D is not a sufficient condition for P

21 definiendum P D P D D is not a necessary condition for P D is not a sufficient condition for P

22 definiendum definiens P D P D D is not a necessary condition for P D is not a sufficient condition for P

23 A bad definition A payment is a wage if and only if It is a transfer of cash from one person to another for services rendered

24 Both defects can occur simultaneously! All the wages are inside this circle

25 All the wages are inside this circle All transfers of cash from one person to another for services rendered are in here

26 Something that is a wage that is not a transfer of cash from one person to another (a check, automatic deposit, etc) All the wages are inside this circle All transfers of cash from one person to another for services rendered are in here

27 Something that is a wage that is not a transfer of cash from one person to another (a check, automatic deposit, etc) Something that is a transfer of cash from one person to another for services rendered but is not a wage (a tip, a one-time payment, etc) All the wages are inside this circle All transfers of cash from one person to another for services rendered are in here

28 he two rows test Definiendum if and only if definiens shows the definiens fails to provide a correct necessary condition for the term to be defined shows the definiens fails to provide a correct sufficient condition for the term to be defined

29 Example item Consider the following inadequate definition: lawnmower =df. a motorized appliance for trimming vegetation that grows in the lawn a.give a counter example that shows that the definition fails to provide a necessary condition for lawnmower. (10 pts) (e.g., the row. Something that is a lawnmower that is not a )

30 Part (b) lawnmower =df. a motorized appliance for trimming vegetation that grows in the lawn b.give a counter example that shows that the definition fails to provide a sufficient condition for lawnmower. (10 pts) (e.g., the row. Something that is a motorized appliance etc. that is not a lawnmower)

31 Another example Consider the following inadequate definition: automobile =df. a four wheeled motorized vehicle a. Give a counter example that shows that the definition fails to provide a sufficient condition for automobile. (10 pts) (e.g., the row. Something that is a four wheeled motorized vehicle that is not an automobile)

32 Part (b) automobile =df. a four wheeled motorized vehicle b.give a counter example that shows that the definition fails to provide a necessary condition for lawnmower. (10 pts) (e.g., the row. Something that is an autmobile that is not a four wheeled motorized vehicle)

33 An infamous definition or purposes of this deposition, a person engages in sexual relations when the person knowingly engages in or causes contact with the *beep*, *beep*, *beep*, *beep*, inner thigh, or *beep* of any person with intent to arouse or gratify the sexual desire of any person. Contact means intentional touching, either directly or through clothing. (Starr Report, Grounds, I.A.1.)

34 or purposes of this deposition, a person engages in sexual relations when the person knowingly engages in or causes contact with the *beep*, *beep*, *beep*, *beep*, inner thigh, or *beep* of any person with intent to arouse or gratify the sexual desire of any person. Contact means intentional touching, either directly or through clothing. (Starr Report, Grounds, I.A.1.) When he testified to the grand jury, the President said that this aspect of the definition still does cover his receiving oral *beep*. he President said that the word cause implies forcing to me and forcible abusive behavior. hus the President said that he did not lie under oath in denying that he caused contact with the *beep* of any person because his activity with Ms. Lewinsky did not include any nonconsensual behavior. (Starr Report, Grounds, ootnote 96).

35 or purposes of this deposition, a person engages in sexual relations when the person knowingly engages in or causes contact with the *beep*, *beep*, *beep*, *beep*, inner thigh, or *beep* of any person with intent to arouse or gratify the sexual desire of any person. Contact means intentional touching, either directly or through clothing. (Starr Report, Grounds, I.A.1.) Concerning oral *beep*, the President s sole answer to the charge that he lied under oath at the deposition focused on his interpretation of any person in the definition.... he President said that by receiving oral *beep*, he would not engage in or cause contact with the *beep*, *beep*, *beep*, *beep*, inner thigh, or *beep* of any person, because any person really means any other person. (Starr Report, Grounds, I.A.6)

36 he President further testified If the deponent is the person who has oral *beep* performed on him, then the contact is with--not with anything on that list, but with the lips of another person. (Starr Report, Grounds, I.A.6) Under the President s interpretation, in an oral *beep* encounter, one person is engaged in sexual relations, but the other person is not engaged in sexual relations. (ibid.)

37 or purposes of this deposition, a person engages in sexual relations when the person knowingly engages in or causes contact with the *beep*, *beep*, *beep*, *beep*, inner thigh, or *beep* of any person with intent to arouse or gratify the sexual desire of any person. Contact means intentional touching, either directly or through clothing. (Starr Report, Grounds, I.A.1.) As to that definition, the President said to the grand jury that he does not and did not believe oral *beep* was covered. Q: Is oral *beep* performed on you within that definition as you understood it, the definition in the Jones-- A: As I understood it, it was not; no. (Starr Report, Grounds, II.B.)