RI Critical Thinking Unit C (Deduction vs Induction) 2023

UNIT C Deduction VS Induction

DEDUCTIVE VS INDUCTIVE ▪ Two main types of arguments: Deductive and Inductive ▪ Deductive: an argument in which the arguer claims/intends that it is impossible for the conclusion to be false given that the premises are true ▪ i.e. the conclusion is claimed to follow necessarilyfrom the premises. ▪ Inductive: an argument in which the arguer claims that it is improbable that the conclusion be false given that the premises are true. ▪ i.e. the conclusion is claimed to follow only probably from the premises. ▪ Deductive arguments involve necessary reasoning ▪ Inductive arguments involve probabilistic reasoning . ▪ Difference: the strength of the argument’s inferential claim is what distinguishes the two.

HOW TO TELL APART? ▪ There are 3 criteria that influence our decision about this claim: ▪ 1) The occurrence of special indicator words like “probably” vs “certainly” ▪ 2) The actual strength of the inferential link between the premises and the conclusion – in other words, does the conclusion follow with 100% probability? ▪ 3) The form or style of the argumentation that the arguer uses (e.g. does the argument go from general to specific?) ▪ Note: The first test is the least indicative of the three. So if it conflicts with the other two tests, ignore it.

STRENGTH OF INFERENTIAL LINK ▪ Deductive: where the conclusion follows necessarily, i.e. with 100% probability from the premises OR impossible for the premises to be true and the conclusion to be false ▪ Inductive: where the conclusion follows probably from the premises OR improbable for the premises to be true and the conclusion to be false

DEDUCTIVE OR INDUCTIVE? ▪ Eg 1 The meerkat is closely related to the suricat. The suricat thrives on beetle larvae. Therefore, the meerkat thrives on beetle larvae. ▪ Eg 2 The meerkat is a member of the mongoose family. All members of the mongoose family are carnivores. Therefore, it follows that the meerkat is a carnivore.

FORM/STYLE OF ARGUMENT ▪ In general… ▪ Deductive: the content of the conclusion is not intended to “go beyond” the content of the premises ▪ Inductive: the content of the conclusion is in some way intended to “go beyond” the content of the premises ▪ This then affects the form or style of the argument that each type can take.

DEDUCTIVE ARGUMENTS: EXAMPLES ▪ An argument that goes from general rules to a specific case ▪ An argument based on mathematics ▪ An argument from definition ▪ Eg 1 All men are mortal Socrates is a man Therefore, Socrates is mortal ▪ Eg 2 2+2=1+1+1+1=4

INDUCTIVE ARGUMENTS: EXAMPLES ▪ An argument that goes from specific instances to general rules ▪ Predictions about the future (based on our knowledge of the past or present) ▪ Arguments from analogy (depends on similarity between two things) ▪ Inductive generalizations (eg.the use of statistical probability to show that as 3 oranges selected from a crate were sweet, the rest of the oranges in that crate are also sweet) ▪ Argum