Description of Composition

The Fallacy of Composition is to conclude that a property shared by a number of individual items, is also shared by a collection of those items; or that a property of the parts of an object, must also be a property of the whole thing.

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.

There are actually two types of this fallacy, both of which are known by the same name (because of the high degree of similarity).

The first type of fallacy of Composition arises when a person reasons from the characteristics of individual members of a class or group to a conclusion regarding the characteristics of the entire class or group (taken as a whole). More formally, the "reasoning" would look something like this.

Individual F things have characteristics A, B, C, etc.
Therefore, the (whole) class of F things has characteristics A, B, C, etc.

This line of reasoning is fallacious because the mere fact that individuals have certain characteristics does not, in itself, guarantee that the class (taken as a whole) has those characteristics.

It is important to note that drawing an inference about the characteristics of a class based on the characteristics of its individual members 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.

The second type of fallacy of Composition is committed when it is concluded that what is true of the parts of a whole must be true of the whole without there being adequate justification for the claim. More formally, the line of "reasoning" would be as follows:

The parts of the whole X have characteristics A, B, C, etc.
Therefore the whole X must have characteristics A, B, C.

That this sort of reasoning is fallacious because it cannot be inferred that simply because the parts of a complex whole have (or lack) certain properties that the whole that they are parts of has those properties. This is especially clear in math: The numbers 1 and 3 are both odd. 1 and 3 are parts of 4. Therefore, the number 4 is odd.

It must be noted that reasoning from the properties of the parts to the properties of the whole is not always fallacious. If there is justification for the inference from parts to whole, then the reasoning is not fallacious. For example, 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. Similarly, if every part of a structure is made of brick, there is no fallacy committed when one concludes that the whole structure is made of brick.

Examples of Composition

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 beans, 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, ice cream, pizza, cake, fish, Jell-O, chicken, taco sauce, soda, oranges, milk, egg rolls, and yogurt so you must like this yummy dish made out of all of them."

"The bicycle is made entirely of low mass components, and is therefore very lightweight."

A related form of fallacy of composition is the "just" fallacy, or fallacy of mediocrity. This is the fallacy that assumes that any given member of a set must be limited to the attributes that are held in common with all the other members of the set. Example:

"Humans are just animals, so we should not concern ourselves with justice; we should just obey the law of the jungle."

Here the fallacy is to reason that because we are animals, we can have only properties which animals have; that nothing can distinguish us as a special case.

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

Rebuttal

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.