Futuristic provided me with another good example for logic type CRs.
Futuristic wrote:
Not all tenured faculty are full professors. Therefore, although every faculty member in the linguistics department has tenure, it must be the case that not all of the faculty members in the linguistics department are full professors.
The flawed pattern of reasoning exhibited by the argument above is most similar to that exhibited by which one of the following?
(A) Although all modern office towers are climate-controlled buildings, not all office buildings are climate-controlled. Therefore, it must be the case that not all office buildings are modern office towers.
(B) All municipal hospital buildings are massive, but not all municipal hospital buildings are forbidding in appearance. Therefore, massive buildings need not present a forbidding appearance.
(C) Although some buildings designed by famous architects are not well proportioned, all government buildings are designed by famous architects. Therefore, some government buildings are not well proportioned.
(D) Not all public buildings are well designed, but some poorly designed public buildings were originally intended for private use. Therefore, the poorly designed public buildings were all originally designed for private use.
(E) Although some cathedrals are not built of stone, every cathedral is impressive. Therefore, buildings can be impressive even though they are not built of stone.
The first step I did is to symbolize the stem:
Not all T are F. All L are T. Therefore not all L are F. The correct conclusion is that it may be true that not all L are F, but it is equally true that all L are F. If we know that all T are L, but not all T are F, then we know for sure not all L are F.
It may be helpful to think the other way. Some Ts are not F. All L are T. But all Ls may be the Ts that are F, or they may be the Ts are not F, we don't know.
So now we know what the error is, then we can proceed.
Quote:
(A) Although all modern office towers are climate-controlled buildings, not all office buildings are climate-controlled. Therefore, it must be the case that not all office buildings are modern office towers.
All M are C. Not all O are C. Therefore not all O are M.
Compare this with the stem.
All L are T. Not all T are F. Therefore not all L are F.
Note L corresponds to M and T corresponds to C. The second condition is not the same.
Quote:
(B) All municipal hospital buildings are massive, but not all municipal hospital buildings are forbidding in appearance. Therefore, massive buildings need not present a forbidding appearance.
All H are M. Not all H are F. Therefore not all H are F.
Again you see the flow is different. Both first and second condition starts with H, while in stem it flows like this: L->T->F.
Quote:
(C) Although some buildings designed by famous architects are not well proportioned, all government buildings are designed by famous architects. Therefore, some government buildings are not well proportioned.
Not all F are W, all G are F. Therefore not all G are W.
Stem:
Not all T are F. All L are T. Therefore not all L are F.
Exactly the same flow.
Quote:
(D) Not all public buildings are well designed, but some poorly designed public buildings were originally intended for private use. Therefore, the poorly designed public buildings were all originally designed for private use.
Not all P are W. Some nonW are U. Therefore all nonW are U.
Not same, don't you think?
Quote:
(E) Although some cathedrals are not built of stone, every cathedral is impressive. Therefore, buildings can be impressive even though they are not built of stone.
Some C are nonS. All C are I. Therefore some nonS can be I.
Again not the same logic.
For this type of questions it is very helpful to symbolize it, then you can ignore the contents and simply compare the logic structure. For this question you don't even need to understand the logic and find the error. Simply translation and comparation would be sufficient. However, it is often very helpful if you could understand why a logic is fause for logical questions.