What Is the Fallacy of Composition?

Fallacies of Ambiguity

The Fallacy of Composition involves taking attributes of part of an object or class and applying them to the entire object or class. It is similar to the Fallacy of Division but works in reverse.

The argument being made is that because every part has some characteristic, then the whole must necessarily also have that characteristic. This is a fallacy because not everything that is true about every part of an object is necessarily true of the whole, much less about the entire class that the object is part of.

One important thing to note is that the Fallacy of Composition is similar to but distinct from the fallacy of Hasty Generalization. This latter fallacy involves assuming that something is true of an entire class due to an atypical or small sample size. This is different from making such an assumption based on an attribute which is indeed shared by all parts or members.

General Form

This is the general form that the Fallacy of Composition takes:

1. All parts (or members) of X have the property P. Thus, X itself has the property P.

Here are some obvious examples of the Fallacy of Composition:

2. Because the atoms of a penny are not visible to the naked eye, then the penny itself must also not be visible to the naked eye.
3. Because all of the components of this car are light and easy to carry, then the car itself must also be light and easy to carry.

It is not the case that what is true of the parts can't also be true of the whole. It is possible to make arguments similar to the above which are not fallacious and which have conclusions which follow validly from the premises. Here are some examples:

4. Because the atoms of a penny have mass, then the penny itself must have mass.
5. Because all of the components of this car are entirely white, then the car itself must also be entirely white.

Characteristics of Arguments

So why do these arguments work - what is the difference between them and the previous two? Because the Fallacy of Composition is an informal fallacy, you have to look at the content rather than the structure of the argument. When you examine the content, you will find something special about the characteristics being applied.

A characteristic can be transferred from the parts to the whole when the existence of that characteristic in the parts is what will cause it to be true of the whole. In #4, the penny itself has mass because the constituent atoms have mass. In #5 the car itself is entirely white because the parts are entirely white.

This is an unstated premise in the argument and depends upon our prior knowledge about the world. We know, for example, that while car parts might be lightweight, getting a whole lot together will likely create something that weighs a lot - and weighs too much to carry easily. A car cannot be made light and easy to carry just by having parts which are, individually, themselves light and easy to carry. Similarly, a penny cannot be made invisible just because its atoms are not visible to us.

When someone offers an argument like the above, and you are skeptical that it is valid, you need to look very closely at the content of both the premises and the conclusion. You may need to ask that the person demonstrates the necessary connection between an attribute being true of the parts and it also ​being true of the whole.

Identifying a Fallacious Argument

Here are some examples that are a little less obvious than the first two above, but which are just as fallacious:

6. Because each member of this baseball team is the best in the league for their position, then the team itself must also be the best in the league.
7. Because cars create less pollution than buses, cars must be less of a pollution problem than buses.
8. With a laissez-faire capitalist economic system, each member of society must act in a way that will maximize his or her own economic interests. Thus, society as a whole will achieve the maximum economic advantages.

These examples help demonstrate the distinction between formal and informal fallacies. The error isn't recognizable simply by looking at the structure of the arguments being made. Instead, you have to look at the content of the claims. When you do that, you can see that the premises are insufficient to demonstrate the truth of the conclusions.

Religion and the Fallacy of Composition

Atheists debating science and religion will frequently encounter variations on this fallacy:

9. Because everything in the universe is caused, then the universe itself must also be caused.
10. "...it makes more sense that there is an eternal God who always existed than to suppose the universe itself has always existed, because nothing in the universe is eternal. Since no part of it lasts forever, then it is only reasonable that all its parts put together were not there forever either."

Aristotle's Human Function

Even famous philosophers have committed the Fallacy of Composition. Here is an example from Aristotle's Nicomachean Ethics:

11. "Is he [man] born without a function? Or as eye, hand, foot, and in general each of the parts evidently has a function, may one lay it down that man similarly has a function apart from all these?"

Here it is argued that, just because the parts (organs) of a person have a "higher function," that, therefore, the whole (a person) also has some "higher function." But people and their organs are not analogous like that. For example, part of what defines an animal's organ is the function it serves - must the whole organism also be defined that way as well?

Even if we assume for a moment that it is true that humans do have some "higher function," it is not at all clear that functionality is the same as the functionality of their individual organs. Because of this, the term function would be used in multiple ways in the same argument, resulting in the Fallacy of Equivocation.

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