Accused of a fallacy? Suspect a fallacy? Ask Dr. Bo and the community!

Quickly register to comment, ask and respond to questions, and get FREE access to our passive online course on cognitive biases!

one moment please...

Fallacy of Composition

(also known as: composition fallacy, exception fallacy, faulty induction)

Description: Inferring that something is true of the whole from the fact that it is true of some part of the whole.  This is the opposite of the fallacy of division.

Logical Form:

A is part of B.

A has property X.

Therefore, B has property X.

Example #1:

Each brick in that building weighs less than a pound.  Therefore, the building weighs less than a pound.

Example #2:

Hydrogen is not wet.  Oxygen is not wet.  Therefore, water (H2O) is not wet.

Example #3:

Your brain is made of molecules.  Molecules do not have consciousness.  Therefore, your brain cannot be the source of consciousness.

Explanation: I included three examples that demonstrate this fallacy from the very obvious to the less obvious, but equally as flawed.  In the first example, it is obvious because weight is cumulative.  In the second example, we know that water is wet, but we only experience the property of wetness when the molecules are combined and in large scale.  This introduces the concept of emergent properties, which when ignored, tends to promote magical thinking.  The final example is a common argument made for a supernatural explanation for consciousness.  On the surface, it is difficult to imagine a collection of molecules resulting in something like consciousness because we are focusing on the properties of the parts (molecules) and not the whole system, which incorporates emergence, motion, the use of energy, temperature (vibration), order, and other relational properties.

Exception: If the whole is very close to the similarity of the parts, then more assumptions can be made from the parts to the whole.  For example, if we open a small bag of potato chips and discover that the first one is delicious, it is not fallacious to conclude that the whole snack (all the chips, minus the bag) will be just as delicious, but we cannot say the same for one of those giant family size bags because most of us would be hurling after about 10 minutes of our chip-eating frenzy.


Goodman, M. F. (1993). First Logic. University Press of America.

Registered User Comments

Become a Logical Fallacy Master. Choose Your Poison.

Logically Fallacious is one of the most comprehensive collections of logical fallacies with all original examples and easy to understand descriptions; perfect for educators, debaters, or anyone who wants to improve his or her reasoning skills.

Get the book, Logically Fallacious by Bo Bennett, PhD by selecting one of the following options:

Not Much of a Reader? No Problem!

Enroll in the Mastering Logical Fallacies Online Course. Over 10 hours of video and interactive learning. Go beyond the book!

Enroll in the Fallacy-A-Day Passive Course. Sit back and learn fallacies the easy way—in just a few minutes per day, via e-mail delivery.

Have a podcast or know someone who does? Putting on a conference? Dr. Bennett is available for interviews and public speaking events. Contact him directly here.

About Archieboy Holdings, LLC. Privacy Policy Other Books Written by Bo
 Website Design and Software Copyright 2017, Archieboy Holdings, LLC.