Definition

The fallacy of Composition is committed when a conclusion is drawn about a whole based on the features of its constituents when, in fact, no justification provided for the inference. That whole may be either an object composed of different parts, or it may be a collection or set of individual members:

• Individual i things have characteristics c₁, c₂, c₃, etc.
• Therefore, the (whole) class of i things has characteristics c₁, c₂, c₃, etc.

• The parts of the whole w have characteristics c₁, c₂, c₃, etc.
• Therefore the whole w must have characteristics c₁, c₂, c₃.

Explanation

This line of reasoning is fallacious because the mere fact that individuals or parts have certain characteristics does not, in itself, guarantee that the class or the whole has those characteristics. It is a special case of identification since it confuses two different levels of abstractions (an individual and a category or a part and a whole).

It is important to note that drawing an inference about the characteristics of a class or of a whole based on the characteristics of its individual members or its parts is not always fallacious. In some cases, sufficient justification can be provided to warrant the conclusion. For example, it is true that an individual rich person has more wealth than an individual poor person. In some nations (such as the US) it is true that the class of wealthy people has more wealth as a whole than does the class of poor people. In this case, the evidence used would warrant the inference and the fallacy of Composition would not be committed. If every part of the human body is made of matter, then it would not be an error in reasoning to conclude that the whole human body is made of matter. Similiarly, if every part of a structure is made of brick, there is no fallacy comitted when one concludes that the whole structure is made of brick.

Examples

The numbers 1 and 3 are both odd. 1 and 3 are parts of 4. Therefore, the number 4 is odd.

A main battle tank uses more fuel than a car. Therefore, the main battle tanks use up more of the available fuel in the world than do all the cars.

A tiger eats more food than a human being. Therefore, tigers, as a group, eat more food than do all the humans on the earth.

Atoms are colorless. Cats are made of atoms, so cats are colorless.

"Every player on the team is a superstar and a great player, so the team is a great team."
This is fallacious since the superstars might not be able to play together very well and hence they could be a lousy team.

"Each part of the show, from the special effects to the acting is a masterpiece. So, the whole show is a masterpiece."
This is fallacious since a show could have great acting, great special effects and such, yet still fail to "come together" to make a masterpiece.

"Come on, you like beef, potatoes, and green beens, so you will like this beef, potato, and green been casserole."
This is fallacious for the same reason that the following is fallacious: "You like eggs, icecream, pizza, cake, fish, jello, chicken, taco sauce, soda, oranges, milk, egg rolls, and yogurt so you must like this yummy dish made out of all of them."

Sodium and Chloride are both dangerous to humans. Therefore any combination of sodium and chloride will be dangerous to humans.
Salt, also known as sodium chloride, is not as dangerous.

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

Germany is a militant country. Thus, each German is militant.

Conventional bombs did more damage in W.W. II than nuclear bombs. Thus, a conventional bomb is more dangerous than a nuclear bomb.

Counter-examples

None.

Advices

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.