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Phil2303 intro to logic.

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Presentation on theme: "Phil2303 intro to logic."— Presentation transcript:

1 phil2303 intro to logic

2 what is ?truth?

3 three 'truth' theories

4 pragmatictheory of truth

5 a statement is true if it allows you to interact effectively and efficiently with the cosmos. the less true a belief is, the less it facilitates such interaction. a belief is false if it facilitates no interaction. in simpler terms: a belief is true if it actually 'works'

6 william james

7 example: my belief that inanimate objects do not spontaneously get up and move about is true because it makes my world more predictable and thus easier to live in.

8 counter example/argument: an isolated indigenous tribe might believe that human sacrifice brings their crops back each year. The crops do come back after the human sacrifice, but not because of the human sacrifice..

9 coherencetheory of truth

10 a statement is true if it is logically consistent with other beliefs that are held to be true. a belief is false if it is inconsistent with (or contradicts) other beliefs that are held to be true. in other words: we should doubt claims that are currently inconsistent with the rest of our beliefs

11 willard quine

12 example: we don't believe in solipsism because it contradicts many of our others sacredly held beliefs.

13 counter example/argument: the universe came into existence five minutes ago complete with historical records and memories

14 correspondencetheory
of truth

15 a claim is true if it corresponds to what is actual (the "facts" or "reality") and false if it does not correspond to what is so. in other words: my beliefs are true if they reflect the way the world really is.

16 bertrand russell

17 example: the statement: 'the opera Aida had its first performance in Cairo' is true just in case the opera Aida had its first performance in Cairo, and false otherwise. "snow is white" is true just in case snow is white.

18 counter example/argument: does the correspondence theory of truth (itself) correspond to the way the world really is, if so- how?

19 Readingassignments {Pirie text} 'ad baculum' arguments page 17
Readingassignments {Pirie text} 'ad baculum' arguments page 17 . 'ad hominem' arguments page 'ad misericordiam' arguments page 109


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