Lesson 31: Division Fallacy

Spot the Faulty Logic #

“Our school has a really good football team. So Jake, who’s on the team, must be a really good player.”

Discussion: Talk with your teacher about this example. Does being part of a good team make every individual member good?

How/Why It’s Often Used #

Just as we might assume parts’ properties transfer to the whole (Composition Fallacy), we might also assume the whole’s properties apply to every part. This can seem reasonable - if a whole has some quality, it’s tempting to assume each component shares it.

This fallacy appears in reasoning about groups, organizations, and categories. People use it to make assumptions about individuals based on group characteristics.

Division Fallacy in Action #

Did you spot the faulty logic? #

A team’s success depends on many factors - some players might be stars, others might be average but fill important roles, and some might be substitutes who rarely play. Being on a good team doesn’t guarantee that each individual is highly skilled.

Second Example #

“Humans are visible to the naked eye. So atoms, which humans are made of, must be visible to the naked eye.”

The Flaw #

A whole can have properties its parts lack. Atoms are far too small to see, even though collections of billions of atoms (people) are visible. Size is not a property that transfers from whole to parts.