1 Chapter 5 pp 192 194 p 199 pp 202 215 Inductive and Deductive Arguments Inductive argument the evidence alone is not enough for the conclusion to be certain even if the premises are true Evidence offers only partial support for the conclusion and consequently you cannot be certain that the conclusion follows So even if the evidence is actually true that the stairs creak and two pervious owners died in accidents the conclusion that the house is haunted might still be false It is because of this uncertainty that the argument is considered inductive On the contrary the real estate agent could say All the houses in Charlestown Massachusetts are haunted o this argument is inherently different than the inductive one o The evidence here if true would force the conclusion to be true o If all houses in Charlestown are haunted and the house at 14 hill street is in Charlestown then the house is haunted o This is a deductive argument the conclusion can be subtracted from the premises Deductive and Inductive arguments share a similarity they both require at least one premise and only one conclusion Key difference involves assessing the relative strength of the arguments What distinguishes a deductive argument is the conclusion is said to follow directly from the premises o No further evidence is needed to support the conclusion At times claims are made without the evidence actually being sufficient o When it is asserted or implied that this set of premises sufficiently supports the conclusion we have a deductive argument If however a conclusion is drawn in spite of missing pieces in the set of premises the argument is inductive Propositions and Value Claims Propositions are either true or false Many use value claims as if they were true but that doesn t make them empirically true We can still use value claims in argents and test the arguments for their strength The key concern in analyzing arguments is the quality if the support the premises give the conclusion if they were presumed true People use value claims al the time The use of them presents problems of verifiability if it is asserted that they are absolutely true or false Propositions The Honda was stolen right in front of Amanda s house A few babies do not like vanilla pudding The red soc made history by winning the World Series in 2004 No peanut is a dairy product 2 Non Propositions Yikes Where s my Tweetie costume Congratulations Value Claims Olive Oyl is not as attractive as Betty Boop There s nothing like the South for delicious Pies Deductive Reasoning A well constructed deductive argument lays the ground work for the conclusion to It is claimed that the conclusion comes right out of the premises follow Prove a case beyond a reasonable doubt demonstrate that the evidence is sufficient to seal the conviction that any reasonable judge should conclude from strength of the evidence that the conclusion follows Goal is to show that there can be no reasonable doubt that the defendants guilt follows from the truth of the premises Some arguments never get off the ground and jurors may not know if each piece of evidence is actually true Generally they cannot know if what is presented in court is really true That task is to decide whether if the evidence is true the conclusion follows Must focus on the reasoning and decide if it hold together under close scrutiny It is the structure of the reasoning that determines a valid argument0 not the truth of the claims The issue of truth comes later when we look are sound arguments The focus is on whether the premises make a ocning cin case for the conclusion Applications of Deductive Reasoning It is a self contained system conclusion come out of the premises If a premise is changed the conclusion changes too Ex 1 No pilot is afraid of heights Some football players are afraid of heights Therefore some football players are not pilots The first premise asserts on characteristics about pilots The second informs us that there are some people football plates who doe not have this characteristic It is argued that those premises are sufficient for the conclusion to come right out of the premises Main types of Deductive Arguments 1 Categorical syllogisms and chains of syllogisms a These are three line arguments consisting of two premises and a conclusion with all of the propositions in the form of categorical propositions b These propositions can be expressed in four possible forms 3 i All A are B ii No A is B iii Some A is B iv Some A is not B c Ex i All romantics cry during sad movies ii No one who cries in a sad movie can eat a lot of popcorn iii Therefore no one who eats a lot of popcorn is a romantic 2 Modus Ponens also true a These are arguments of the form If A then B A is the case Therefore B is i The first premise is conditional claim ii The second affirms that the antecedent is true iii The conclusion is that the consequent must also be true b Ex i ii The dentist slipped while operating iii Omar will need stitches If the dentist slips while operating Omar will need stitches 3 Modus Tollens a These are arguments of the form If A then B B is not the case Therefore A is not true either i First premise is a conditional claim ii Second is denies the consequent by saying it is not true iii The inference then is that the antecedent cannot be true b Ex i b Ex If Bruce gets a tattoo of a dragon his mother did not go through the roof ii Bruce s mother did not go through the roof iii Brice did not get a tattoo of a dragon 4 Disjunctive Syllogism Either Or a Of the form of Either A or B A is not the case Therefore B must be true Or Either A or B B is not true Therefore A must be true i Either that s a rainbow trout or a weird looking salmon ii That s not a rainbow trout iii So it s a weird looking salmon 5 Hypothetical Syllogism a Arguments of the form If A then B If B then C Therefore if A then C b Ex i ii iii If Louie goes to the powwow hell miss the ball game If Louie misses the ball game he won t get a chili dog If Louie goes to the powwow he wont get a chili dog c Also can be expressed as All A is B All B is C Therefore all A is C 4 d Ex b Ex b Ex d Ex i Anyone who enjoys music will like my new Taylor Swift album ii Anyone who like my new Taylor Swift album will like Loreen iii Therefore anyone who enjoys music will like Loreena McKennit McKennit 6 Constructive Dilemma a Take the form of If A then B and if C then D Either B or D …