Propositions and Arguments What is a proposition A

  • Slides: 11
Download presentation
Propositions and Arguments

Propositions and Arguments

What is a proposition? • A proposition is a predicative sentence that only contains

What is a proposition? • A proposition is a predicative sentence that only contains a subject and a predicate S is P.

Which of these sentences express propositions? 1. 2. 3. 4. 5. 6. 7. 8.

Which of these sentences express propositions? 1. 2. 3. 4. 5. 6. 7. 8. 9. Sydney is north of Melbourne. Is Edinburgh in Scotland? The moon is made of swiss cheese. Did you see the eclipse? What an eclipse! Would that I were good at logic. Look at the eclipse. I wish that I were good at logic. 7+12=23

Arguments • Arguments in everyday situations take place between people. • Arguments give reasons

Arguments • Arguments in everyday situations take place between people. • Arguments give reasons for believing the truth of a proposition. • Logic studies the information content of these arguments.

• An argument is a list of propositions, called the • premises, •

• An argument is a list of propositions, called the • premises, • followed by a word such as ‘therefore’, or ‘so’, and then another proposition, called the conclusion. • The reason for accepting the information in the conclusion is based on the premises. • If everything is determined, people are not free. Premise • People are free. Premise • So not everything is determined. Conclusion

Rule Individual instances INDUCTIVE Arguments Rule Individual instances DEDUCTIVE Arguments

Rule Individual instances INDUCTIVE Arguments Rule Individual instances DEDUCTIVE Arguments

Rule Most Hungarians commit tax fraud. Gábor is Hungarian. So, Gábor is likely to

Rule Most Hungarians commit tax fraud. Gábor is Hungarian. So, Gábor is likely to commit tax fraud. • The link between the premises weaker. • The truth of the premises only makes the truth of the conclusion , but does not guarantee it • The conclusion is only possibly true. • These arguments are Inductive arguments. Individual instances INDUCTIVE Arguments

All Hungarians commit tax fraud. Gábor is Hungarian. So, Gábor commits tax fraud. Rule

All Hungarians commit tax fraud. Gábor is Hungarian. So, Gábor commits tax fraud. Rule The premises support the truth of the conclusion: it is impossible for the premises to be true and the conclusion to be false. These are called deductive arguments. Hungarians People commiting tax fraud Individual instances DEDUCTIVE Arguments

Valid arguments • An argument is valid if and only if whenever the premises

Valid arguments • An argument is valid if and only if whenever the premises are true, so is the conclusion. • In other words, it is impossible for the premises to be true while at the same time the conclusion is false.

Sound arguments • An argument is sound, just in the case where it is

Sound arguments • An argument is sound, just in the case where it is valid, and, in addition, the premises are • all true. So, the conclusion of a sound argument must also be true. • soundness appeals to the truth of the matter.

Valid Argument Scheme All bats are birds. All birds fly. H H Not sound

Valid Argument Scheme All bats are birds. All birds fly. H H Not sound -----------------Therefore all bats fly. All whales are mammals. All mammals have hearts. I B I I -----------------All whales have hearts. c A I Sound C All A’s are B’s All B’s are C’s --------So all A’s are C’s

propositions proposition 1 agents need content proposition 2propositions proposition 1 agents need content proposition 2
VALUE PROPOSITION Value Proposition Value proposition is aVALUE PROPOSITION Value Proposition Value proposition is a
VALUE PROPOSITION Value Proposition Value proposition is aVALUE PROPOSITION Value Proposition Value proposition is a
Effective Arguments Writing Persuasive PrincipleBased Arguments Effective ArgumentsEffective Arguments Writing Persuasive PrincipleBased Arguments Effective Arguments
Design Arguments Arguments for theism Ontological arguments CosmologicalDesign Arguments Arguments for theism Ontological arguments Cosmological
Command Line Arguments Command Line Arguments Arguments providedCommand Line Arguments Command Line Arguments Arguments provided
Inductive Arguments Arguments n Two kinds of argumentsInductive Arguments Arguments n Two kinds of arguments
Sense STRUCTURED PROPOSITIONS Structured Propositions Like Sof AsSense STRUCTURED PROPOSITIONS Structured Propositions Like Sof As
Propositions The combination of propositions Dr Retno PurwaniPropositions The combination of propositions Dr Retno Purwani
SIX PROPOSITIONS RATHER UNUSUAL PROPOSITIONS ABOUT Critical threatsSIX PROPOSITIONS RATHER UNUSUAL PROPOSITIONS ABOUT Critical threats