Another form in which the fallacy of the undistributed middle appears in a manner less easy to detect is shown by the following syllogism:
1. All orators are men of great ability.
2. Herbert Lang is a man of great ability.
3. Therefore Herbert Lang is an orator.
Each of the premises in the above syllogism may be perfectly true as a matter of fact, but it is obvious that there is something wrong with the syllogism as a whole. The nature of the defect is not apparent until we begin to apply the rules for constructing a valid syllogism. This reveals the fact that instead of the major term including the middle term, the middle includes the major. If we diagram the major premise by the system of circles previously employed the following result is obtained:
If the conclusion to be established had been that Herbert Lang is a man of great ability and the minor premise had stated that Herbert Lang was an orator then the major premise as outlined above would have been perfectly valid. But the conclusion that Herbert Lang is an orator does not follow from the fact that he is a man of great ability and that all orators are men of great ability. The only fact that we can draw from these statements is that some men of great ability are orators. Because we say that all orators are men of great ability we cannot be sure of the converse, that is, that all men of great ability are orators. Only some of them are orators, others may be ministers, doctors, lawyers, or business men. Therefore all that we can conclude is that, “Some men of great ability are orators.” It is now plain that when we construct the completed syllogism from this major premise, the same defect will exist which was revealed in the preceding illustration.
1. Some men of great ability are orators.
2. Herbert Lang is a man of great ability.
3. Therefore Herbert Lang is an orator.