Let's say someone states "One well-known property of tables is that they are supported by four legs. This chair is supported by four legs. So this chair is a table".
What kind of fallacy would this be?
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This is called the fallacy of composition. Take an extreme example: "All tables are made from wood and this toy is made from wood. Therefore this wooden toy was made from a table!" There are multiple fallacies there actually but you see the point. Another one: Because human being DNA is 99.99 percent identical to Chimpanzee DNA doesn't mean human beings are chimpanzees correct? Another version is "this folding chair is made of metal. Therefore every part of the folding chair must also be made from metal. Well is the seat cushion also made of metal? Seems that would not be comfortable. :)– LogikalCommented Jun 23, 2021 at 20:21
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This is not the fallacy of composition. The fallacy of the question is "all X's are P and all Y's are P so all Y's are X's. The fallacy of composition is "all parts of x are P so x is P".– David GudemanCommented Jun 23, 2021 at 20:45
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2 Answers
answered Jun 23, 2021 at 16:12
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What is the undistributed middle in the case of four legs? The legs themselves? While the chairs and tables are left and right? Commented Jun 23, 2021 at 23:05
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@Deschele - having four legs. We use properties (predicates) in syllogism Commented Jun 25, 2021 at 6:51
The reasoning falsely implies that sharing a property means being the same. This can be the case, though it's not in general.
Obviously, a proton and a positron are not the same while having the same charge. If only attention is paid to electric charge then both are the same though.
It's called a context dependent fallacy. If more properties than the equated properties are considered then a fallacy can arise. If not the properties can be equal or not. So four legs are four legs but a chair is not a table. Two charges can be opposite but the particles can be the same (or not, depending on your view of the particle which is the context)..
