When a property of a part is attributed to the whole, or a property of the whole is attributed to its parts, without sufficient evidence to justify such a generalisation.
Definition:
This fallacy occurs in two main forms:
- Composition: Assuming that if every part of a whole has a certain property, then the whole must also have that property.
- Division: Assuming that if the whole has a certain property, then each of its parts must also have that property.
These assumptions become fallacious when there is no necessary connection between the properties of the parts and the whole.
Typical structure of this fallacy:
- Composition:
- Each part of X has property P.
- Conclusion: The whole X has property P.
- Each part of X has property P.
- Division:
- The whole X has property P.
- Conclusion: Each part of X has property P.
- The whole X has property P.
Examples from real life:
1. In politics (Composition):
a) “Every member of this party, including John and Anna, is honest and trustworthy; therefore, the party is effective.”
Here, it should be noted that the structure and performance of a party can be influenced by factors other than the honesty of its members.
b) “All members of this council, including Peter and Maria, are educated; therefore, the council makes wise decisions.”
Here, it should be noted that the education of members alone does not guarantee the quality or wisdom of all council decisions. What can provide such a guarantee is the kind of education described in the second paragraph of Article 26 of the Universal Declaration of Human Rights—education aimed at the full development of the human personality and the strengthening of respect for human rights and freedoms. Without such education, even educated people may make unwise or unjust decisions.
c) “Every minister in this government, including David and Anna, has extensive management experience; therefore, the government will always perform successfully.”
Here, it should be noted that the overall performance of a government depends on complex factors that go beyond the individual experience of a few ministers.
2. In the media (Division):
“This newspaper, of which Linda is the editor, is reputable; therefore, every article published in it is reliable.”
Here, it should be noted that even reputable media outlets can sometimes publish inaccurate or biased material.
3. In science (Composition):
“Every researcher in this institute, including Thomas and Sara, is an expert in their field; therefore, the institute is flawless in all areas of science.”
Here, it should be noted that individual ability does not necessarily guarantee complete success in group work.
3. In daily life (Division):
“This football team is very successful; therefore, every player in it must be a superstar.”
Here, it should be noted that a team’s success may be the result of cooperation and collective coordination rather than the individual brilliance of every member.
Why is this fallacy dangerous?
- It weakens precision in reasoning: By oversimplifying, it ignores the complex reality of the relationship between part and whole.
- It creates false generalisations: It may lead to conclusions unsupported by sufficient evidence.
- It influences public decision-making: In politics, media, or business, it can be used to mislead public opinion.
How can we recognise and respond to it?
If you hear that a property of a part or a whole is being generalised to the other, ask:
– Is there a necessary relationship between the property of the part and that of the whole?
– Is there independent evidence to support this generalisation?
– Does this property exist in all parts or only in some?
– Even if every member of a group has a positive trait, such as honesty, can that trait guarantee the success of the whole group?
A suitable response might be: “The fact that a part has a property does not necessarily mean that the whole has it (or vice versa). Let’s examine independent evidence for this claim and assess all aspects.”
Conclusion:
The composition/division fallacy results from wrongly generalising properties between part and whole, leading to flawed reasoning. Recognising this fallacy helps us examine arguments more carefully and avoid hasty conclusions.