Composition, Fallacy of

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The fallacy of Composition is committed when a conclusion is drawn about a whole based on the qualities of its parts without a justification provided for the inference. There are two types of this fallacy.

The first type occurs when a conclusion about an entire group is inferred from the characteristics of individual members that group. The reasoning looks like this:

 

Premise 1: Individual F things have characteristics A, B, C, etc.

Conclusion: Therefore, the whole group of F things has characteristics A, B, C, etc.

 

This is fallacious because the fact that individuals have certain characteristics does not, by itself, guarantee that the group (taken as a whole) has those characteristics.

Drawing an inference about the characteristics of a class based on the characteristics of its individual members is not always fallacious. If sufficient evidence is provided for the conclusion, no fallacy would be committed.

The second type is committed when it is concluded that what is true of the parts must be true of the whole without adequate justification for the claim. More formally, reasoning is as follows:

 

Premise 1: The parts of the whole X have characteristics A, B, C, etc.

Premise 2: Therefore, the whole X must have characteristics A, B, C.

 

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

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 this fallacy would not be committed. 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.

 

Defense:  The key to avoiding this fallacy is to be cautious about inferences from parts to wholes. If the inference is made without justification, then this fallacy has occurred.

 

Example #1

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.

 

Example #2

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 as a group.

 

Example #3

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

 

Example #4

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.

 

Example #5

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.

 

Example #6

Come on, you like beef, potatoes, and green beans, so you will like this beef, potato, and green bean 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 from all of them.

 

Example #7

Sodium and chlorine are both dangerous to humans. Therefore, any combination of sodium and chlorine will be dangerous to humans.

 

Example #8

“I checked all the parts of my PC, and each part is good. So, once I get it assembled, the whole PC will work just fine.”

Originally appeared on A Philosopher’s Blog Read More

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