notes_3_2x2 - Branden Fitelson Philosophy 12A Notes 1...

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Unformatted text preview: Branden Fitelson Philosophy 12A Notes 1 Announcements & Such Coldplay : two tracks from Viva La Vida Administrative Stuff If you did not receive an email telling you which section you are in, then you are not going to be enrolled in the course this semester (unless we made an error, in which case, see us at end of class). Section rosters have been set (see website for times and locations). Sections with (as yet) undetermined permanent locations will meet temporarily in 301 Moses. Stay tuned for permanent locations. HW #1 (1 st sub) due Friday @ 4pm @ 12A drop box (301 Moses). Introduction to the Course & Chapter 1 of Forbes My Big Picture (one more time) Are our two renditions/definitions of validity really equivalent? * Our first glimpse of a fundamental idealization of (classical) logic. Working with our official (idealized) definition of validity. UCB Philosophy Introduction & Chapter 1 09/03/08 Branden Fitelson Philosophy 12A Notes 2 Abstract Argument Logical Form LSL / LMPL / LFOL Symbolization Chapters 2, 5 & 7 English Argument Valid Form? Deciding Formal Validity Chapters 3, 4, 6 & 8 Valid English Argument? Valid Abstract Argument? Articulation of Thought in English UCB Philosophy Introduction & Chapter 1 09/03/08 Branden Fitelson Philosophy 12A Notes 3 Our Two Renditions of Validity Are They Equivalent? Informally, if the conclusion of an argument follows from its premises, then the argument is said to be valid (otherwise, its in valid). It is this informal (Forbes calls it absolute) validity concept that were interested in. Plausibly, this can be made more precise, as follows: Definition #1 . An argument A is valid if and only if: It is (logically!) necessary that if all of the premises of A are true, then the conclusion of A is also true. Definition #2 . An argument A is valid if and only if: It is (logically!) impossible that both : (1) all of the premises of A are true, and (2) the conclusion of A is false. I mentioned las time that, for us, these two definitions are equivalent , and that well take #2 as our official definition. Lets think about a pair of limiting cases of #2, which will reveal a fundamental idealization . UCB Philosophy Introduction & Chapter 1 09/03/08 Branden Fitelson Philosophy 12A Notes 4 Two Strange Validities Under Our Official Definition #2 ( ) p . Therefore, either q or not q . ( ) is valid because it is (logically) impossible that both : (i) p is true, and (ii) either q or not q is false. This is impossible because (ii) alone is impossible....
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This note was uploaded on 09/23/2009 for the course PHIL 12A taught by Professor Fitelson during the Spring '08 term at University of California, Berkeley.

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notes_3_2x2 - Branden Fitelson Philosophy 12A Notes 1...

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