Lecture Notes by Christopher Lay

Los Angeles Pierce College

Department of History, Philosophy, and Sociology

 

 

 

 

Mathew Van Cleave's 2016 Introduction to Logic and Critical Thinking

 

https://open.umn.edu/opentextbooks/BookDetail.aspx?bookId=457

 

 

 

 

Chapter 1 "Reconstructing and Analyzing Arguments"

§8 "Deductive and Inductive Arguments "

" A deductive argument is an argument whose conclusion is supposed to follow from its premises with absolute certainty ... ." 

 

In a deductive argument, there is "no possibility that the conclusion doesn’t follow from the premises."

 

"[A]n inductive argument is an argument whose conclusion is supposed to follow from its premises with a high level of probability ... ." 

 

This "means that although it is possible that the conclusion doesn’t follow from its premises, it is unlikely that this is the case." 

 

 

 

 

 

 

 

 

 

Inductive Arguments

In an inductive argument, "the premises [are supposed to] give us a strong reason for accepting the conclusion." 

 

"This is true even though we can imagine a scenario in which the premises are true and yet the conclusion is false." 

 

 

 

 

 

 

 

 

 

 

Defeasible, and the Strength of Inductive Arguments

"[I]nductive arguments are defeasible arguments since by adding further information or premises to the argument, we can overturn (defeat) the verdict that the conclusion is well-supported by the premises." 

 

[Defeasible is defined by the Oxford Dictionary of American English as "open in principle to revision, valid objection, forfeiture, or annulment."]

 

"Inductive arguments whose premises give us a strong, even if defeasible, reason for accepting the conclusion are called, unsurprisingly, strong inductive arguments."

 

"[A]n inductive argument that does not provide a strong reason for accepting the conclusion are called weak inductive arguments." 

 

"Valid deductive arguments" are not defeasible.