Division – assuming that complex parts can be removed, but retain their integrity.
 

The reverse of the composition fallacy, the fallacy of division suggests that complex ideas can be divorced from their unified situations and still maintain their strength alone.  To state that the average American family will have 1.8 children, for example, does not mean that your sister and brother-in-law are likely to have 1.8 children each.  The average number is simply that — an average.  It does not predict how many children may be born into your family specifically.  The division is a form of overgeneralization.
 

EXAMPLE

An idealist speaks: “Purdue is a great engineering school.  Mike went there; he must be a great engineer.”

The claim that Purdue is a strong engineering school can be supported by evidence.  In every college, though, there is at least one student who does not perform well, but somehow manages to earn a degree.  People are sometimes also admitted into colleges for alternate reasons than academic performance.  Just because one student happens to belong to a group does not mean that he will display the qualities found in the reputation of the entire school.  In this example, the Purdue graduate will probably rely on his school’s name to impress his future supervisors and clients, rather than his talents as an engineer.