Composition and Division

Fallacies of Composition and Division	Close Window

Fallacy of composition takes the attributes of particulars and claims that the attributes also describe the group. For instance, if someone notes that most of the people in Peterson's critical thinking class are excellent students that most of the people at SRJC are excellent students.

Fallacy of division makes the mistake of saying that the particular members of a group have the same attributes as the group. For instance, one might say that because Peterson's 5:00 class is above average in performance, that Joe Hockenmyer (a student in that class) is above average.

Explanation of Fallacy of Composition

Because the parts of a whole have a certain property, it is argued that the whole has that property. That whole may be either an object composed of different parts, or it may be a collection or set of individual members.

Examples:

(i) Each brick is three inches high, thus, the brick wall is three inches high.

(ii) Paul Goldschmidt, Bryce Harper, Nelson Cruz, Josh Donaldson, Adrian Gonzalez, Dallas Keuchel, Sonny Gray, Anthony Rizzo, Matt Carpenter, Justin Upton, Jason Kipnis, Felix Hernandez, Chris Archer, Zack Greinke, Stephen Vogt, Dee Gordon, Andrew Miller, Mike Trout, Joc Pederson, A.J. Pollock, Max Scherzer, Prince Fielder, Gerrit Cole, Miguel Cabrera, and Drew Storen are the best players in Major League Baseball, so if they were on the same team, they’d win the World Series. (Rankings in June 2015.)

(iii) Conventional bombs did more damage in W.W. II than nuclear bombs. Thus, a conventional bomb is more dangerous than a nuclear bomb. (From Copi, p. 118)

Proof:

Show that the properties in question are the properties of the whole, and not of each part or member or the whole. If necessary, describe the parts to show that they could not have the properties of the whole.

Explanation of Fallacy of Division

Because the whole has a certain property, it is argued that the parts have that property. The whole in question may be either a whole object or a collection or set of individual members.

Examples:

(i) The brick wall is six feet tall. Thus, the bricks in the wall are six feet tall.

(ii) Because the brain is capable of consciousness, each neural cell in the brain must be capable of consciousness.

(iii) Germany is a militant country. Thus, each German is militant.

Proof:

Show that the properties in question are the properties of the parts, and not of the whole. If necessary, describe the parts to show that they could not have the properties of the whole.

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