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"

§4 "More Complex Argument Structures"

"[V]ery often arguments and explanations have a more complex structure than just a few premises that directly support the conclusion."

"[A]rguments can have ... different structures and ... some arguments will be longer and more complex than others." 

"Determining the structure of very complex arguments is a skill that takes some time to master." 

"[R]emember that any argument structure ultimately traces back to some combination of" the following structures. 

Complex Arguments' Main Conclusions

"The main conclusion of [an] argument ... is the statement that depends on other statements as evidence but doesn’t itself provide any evidence for any other statement."

Determining the Structure of a Complex Argument

"To determine the structure of an argument, we must determine which statements support which. We can use our premise and conclusion indicators to help with this."

Intermediate Conclusions

In a complex argument, some statements provide "evidence directly for the main conclusion, but [those statements are] supported by another statement." 

An intermediate conclusion is supported by a reason, and an intermediate conclusion also supports some other, further claim.  "[O]ne and the same statement can act as both a premise and a conclusion."

"from"

(Note: when we want to say that some “statement follows from statement #" we say "from #."  "We will use this convention as a way of keeping track of the structure of the argument.") 

Sub-Arguments and Main Arguments

" A subargument, as the term suggests, is a part of an argument that provides indirect support for the main argument. The main argument is simply the argument whose conclusion is the main conclusion."

Arguments with Independent Support

"Another type of structure that arguments can have is when two or more premises provide direct but independent support for the conclusion."

Exercise 4

"Write the following arguments in standard form and show how the argument is structured." 

3. "There was someone in this cabin recently because there was warm water in the tea kettle and because there was wood still smoldering in the fireplace. But the person couldn’t have been Tim because Tim has been with me the whole time. Therefore, there must be someone else in these woods."

"Write the following arguments in standard form and show how the argument is structured." 

4. "It is possible to be blind and yet run in the Olympic Games since Marla Runyan did it at the 2000 Sydney Olympics."

"Write the following arguments in standard form and show how the argument is structured." 

5. "The train was late because it had to take a longer, alternate route since the bridge was out."