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 4 "Informal fallacies", § 1 "Formal vs. Informal Fallacies," Sub-§ 2 "Division Fallacy"

"The division fallacy is like the composition fallacy ... ." 

 

"[I]n order to identify informal fallacies (like composition and division), we must rely on our understanding of the concepts involved in the argument." 

 

This means that "an argument that has the same form ... doesn’t [necessarily] commit the division fallacy." 

 

 

 

 

 

 

 

 

 

Division: From Whole to Parts

"The difference is that the division fallacy argues that since the whole has some feature, each part must also have that feature."  

 

"The composition fallacy, as we have just seen, goes in the opposite direction: since each part has some feature, the whole must have that same feature."   

 

 

 

 

 

 

 

 

 

 

The Fallacy

"Just because the whole [has a property], it doesn’t follow that each part of the [whole has the same properties]." 

 

 

 

 

 

 

 

 

 

Examples

Is this a fallacy?    

1) Salt is good!  Sodium must be just as good–and chlorine too! 

 

 

 

 

 

 

 

 

 

Examples

Is this a fallacy?   

2) Altogether, the student body at Pierce College weighs around 42,281 pounds.  So, every single student should rethink their caloric intake. 

 

 

 

 

 

 

 

 

 

Examples

Is this a fallacy?   

3)  The entire ceiling in this room is thirty feet wide.  Thus, each part of the ceiling in this room is thirty feet wide.

 

 

 

 

 

 

 

 

 

Examples

Is this a fallacy?   

4)  The entire ceiling is a shade of white.  Therefore, each part of the ceiling is a shade of white.