1.3 and 1.4 Notes PDF

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1.3 and 1.4 Notes Fall 2018...

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Deductive argument ● An argument incorporating the claim that it is IMPOSSIBLE for the conclusion to be false given that the premises are true ● If the premises are true, then the conclusion is necessarily true ● Conclusion should not have more information than the premises ○ Info in conclusion should already be in the premises Inductive argument ● An argument incorporating the claim that it is IMPROBABLE that the conclusion be false given that the premises are true ● If the premises are true, then the conclusion is probably true Features to decide if an argument is deductive or inductive ● Occurence of special indicator words ○ DEDUCTIVE ■ Necessarily ■ Certainly ■ Absolutely ■ Definitely ○ INDUCTIVE ■ Probably ■ Improbable ■ Plausible ■ Implausible ■ Likely ■ Unlikely ■ Reasonable to conclude ● The actual strength of the inferential link between premises and conclusion ○ Absolute or only probable support for the conclusion ● Form or style of argumentation ○ Definiton in it? Have a cause and effect? Formal syllogism? Etc ○ Try to identify these DEDUCTIVE Argument based on mathematics ● Argument in which the conclusion depends on some purely arithmetic or geometric computation or measurement ● Like mathematical proofs Argument from definition ● Argument in which the conclusion is claimed to depend merely on the definition of some word or phrase used in the premise or conclusion ● P1= bachelor means unmarried man ● P2 = bob is a bachelor ● C= Bob is unmarried Syllogism (formal inference)→ 2 premises and 1 conclusion ● Inferences that are judged to be good, solely based on their logical forms ● Anything in the following form is good

● All As are Bs ● All Bs are Cs ● Therefore all As are Cs Categorical syllogism ● Each statement begins with “all”, “no”, or “some” Hypothetical syllogism ● Has a conditional statement for one or both of its premises Disjunctive syllogism ● Has a disjunctive (either...or) statement ● Two options → remove one, therefore has to be the other ○ A or B /// Not A /// Therefore B INDUCTIVE Prediction ● An argument that proceeds from our knowledge of the past to a claim about the future ● Infers something about the future from our knowledge of the past ○ Future can not be known with certainty Argument from analogy ● An argument that depends on the existence of an analogy or similarity between two things or state of affairs ● Inference based on relevant similarities between two things Generalization ● An argument that proceeds from the knowledge of a selected sample to some claim about the whole group Argument from authority ● An argument that concludes something is true because a presumed expert or witness has said that it is ○ But they cant know everything Argument based on signs ● An argument that proceeds from the knowledge of a sign to a claim about the thing or situation that the sign symbolizes (ex. A road sign) ○ Not all signs are correct (misleading) ○ The same sign can mean different things in different contexts Causal inference ● An argument that proceeds from knowledge of a cause to a claim about an effect, or conversely, from knowledge of an effect to a claim about a cause ○ ex) i left a piece of cake in the fridge but now it is gone. Probably my roommate ate it (effect to its cause) ○ My roommate said that she ate a piece of cake today. Probably the cake I left in the fridge is gone (cause → effect) particular statement ● One that makes a claim about one or more particular members of a class General statement ● Makes a claim about all the members of a class

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Validity and soundness ○ Good properties for deductive arguments Invalidity and unsoundness ○ Bad properties for deductive arguments Strength and cogency ○ Good properties for inductive arguments Weakness and uncogency ○ Bad properties for inductive arguments

Valid , Weak inductive argument ● An argument in which the conclusion does not follow probably from the premises, even though it is claimed to ● It is not improbable that the conclusions is false even if all the premises are true Cogent argument ● An inductive argument that is strong and has all actually true premises and meets total evidence requirement ○ Reflects all the important factors Uncogent argument ● An inductive argument that is weak, has one or more false premises, fails to meet the total evidence requirement, or a combo ● Strong argument and has false premise Uniformity of nature ● The future replicates the past and regularities that prevail in one spatial region tend to prevail in other regions too ○ ex) sugar is sweet -->was sweet, will be sweet next time; will be sweet in new york or london 2 questions ● Do the premises support the conclusion? ● Are all the premises true? ○ Begin by assuming all the premises are true ****tables/flowcharts are helpful pg 53 ● ● ●

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All sound arguments are valid arguments Valid arguments can have false premises Sound arguments CANNOT have false conclusions ○ Sound arguments are valid ○ Valid = all premises are true, so conclusion has to be true as well Unsound arguments can have true conclusions

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A sound argument cannot be made unsound by adding a premise *** Inductive strength corresponds to deductive validity ○ Weakness corresponds to invalidity Inductive cogency corresponds to deductive soundness ○ Uncogency corresponds to unsoundness...