Fallacy of The Undistributed Middle
The fallacy of the undistributed middle is a fallacy that is committed when the middle term in a categorical syllogism is not distributed. It is thus a syllogistic fallacy. More specifically it is also a form of non sequitur.
The fallacy of the undistributed middle takes the following form:
- All Zs are Bs.
- Y is a B.
- Therefore, Y is a Z.
It may or may not be the case that "all Zs are Bs," but in either case it is irrelevant to the conclusion. What is relevant to the conclusion is whether it is true that "all Bs are Zs," which is ignored in the argument.
Note that if the terms were swapped around in the first co-premise then it would no longer be a fallacy, although it could still be unsound. This also holds for the following two fallacies which are similar in nature to the fallacy of the undistributed middle and also non sequiturs.
An example can be given as follows:
- All men are humans.
- Mary is human.
- Therefore, Mary is a man.
Read more about this topic: Non Sequitur (logic)
Famous quotes containing the words fallacy of the, fallacy of, fallacy and/or middle:
“I’m not afraid of facts, I welcome facts but a congeries of facts is not equivalent to an idea. This is the essential fallacy of the so-called “scientific” mind. People who mistake facts for ideas are incomplete thinkers; they are gossips.”
—Cynthia Ozick (b. 1928)
“I’m not afraid of facts, I welcome facts but a congeries of facts is not equivalent to an idea. This is the essential fallacy of the so-called “scientific” mind. People who mistake facts for ideas are incomplete thinkers; they are gossips.”
—Cynthia Ozick (b. 1928)
“It would be a fallacy to deduce that the slow writer necessarily comes up with superior work. There seems to be scant relationship between prolificness and quality.”
—Fannie Hurst (1889–1968)
“The middle years of parenthood are characterized by ambiguity. Our kids are no longer helpless, but neither are they independent. We are still active parents but we have more time now to concentrate on our personal needs. Our children’s world has expanded. It is not enclosed within a kind of magic dotted line drawn by us. Although we are still the most important adults in their lives, we are no longer the only significant adults.”
—Ruth Davidson Bell. Ourselves and Our Children, by Boston Women’s Health Book Collective, ch. 3 (1978)