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Unformatted text preview: Branden Fitelson Philosophy 12A Notes 1 $ % Overview of Today’s Lecture • Bob Marley, Acoustic Medley • Administrative Stuff – I went over the syllabus/website last time. See website for all details: * http://fitelson.org/12A/ – If you weren’t here last time, (a) please get a syllabus, and (b) fill-out an index card with your section preferences, among these 6 pairs: * (1) 10–11 MW, (2) 12–1 MW, (3) 10–11 TR (4) 11–12 TR (5) 1–2 MW, (6) 2–3 MW – See us after class if you have questions about the sections, etc. • Introduction to the Course & Chapter 1 of Forbes – Propositions — the basic building blocks of logical analysis – Actual truth and falisty vs possible/necessary truth and falsity – Logical necessity, logical truth, validity, and soundness UCB Philosophy Introduction & Chapter 1 01/21/10 Branden Fitelson Philosophy 12A Notes 2 ' & $ % Background 1: Propositions and Sentences • Propositions are the basic units of logical analysis. They are expressed by declarative sentences like “Snow is white.” • Not all sentences express propositions ( e.g. , “What time is it?”). • Propositions are not identical to declarative sentences that express them. Consider: “Snow is white” and “Schnee ist weiß.” • Propositions are either true or false (not both). True and False are called truth-values . Propositions have exactly one truth-value. The truth-value of a proposition is objective . • That is, whether a proposition is true or false (in a given situation) does not depend on what anyone thinks about that proposition or on how that proposition happens to be expressed. • Even if a proposition is about something subjective, its truth-value remains objective ( e.g. , Branden believes that the Yankees will win.) UCB Philosophy Introduction & Chapter 1 01/21/10 Branden Fitelson Philosophy 12A Notes 3 $ % Background 2: Actual, Possible, and Necessary Truth • Some propositions are actually true (Snow is white), and some are not (Al Gore is President of the United States in 2007). • Other propositions are not actually true, but still possibly true. Al Gore is not actually our President in 2007, but he might have been . As such, it is possibly true that Al Gore is President in 2007. • Some propositions are not even possibly true. For instance: 1. My car has traveled faster than the speed of light. 2. 2 + 2 = 5. 3. Branden weighs 200 lbs and Branden does not weigh 200 lbs. • (1) violates the laws of physics: it is physically impossible . (2) violates the laws of arithmetic: it is arithmetically impossible. • (3) violates the laws of logic : it is logically impossible. UCB Philosophy Introduction & Chapter 1 01/21/10 Branden Fitelson Philosophy 12A Notes 4 ' & $ % • This is the kind of impossibility that interests the logician. In slogan form, we might call this “the strongest possible kind of impossibility.” • Some propositions are not only actually true, but (logically) necessarily true. Thesetrue....
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This note was uploaded on 04/20/2010 for the course PHIL 63170 taught by Professor Fitelson during the Spring '10 term at Berkeley.
- Spring '10