Discussion
If the "Fishologist's" statements are true, which of the following can be concluded?
*This question is included in Exercise Set 1: Intro to Conditionals, question #7
| (A) | The strange-looking creature cannot walk on land. |
| (B) | ... |
| (C) | ... |
| (D) | ... |
| (E) | ... |
| (F) | ... |
The solution is
Posted: 10/04/2011 15:37
Hi I don't understand why D is wrong. Could you explain it to me. Thanks
Posted: 10/05/2011 22:31
The reason that choice "D" is wrong is that the two conditionals do not have any bearing on one another.
What do I mean by this? Let's check out the diagrams for both statements.
Premise 1: "All swordfish swim in the sea"
This becomes: SF → SS
Premise 2: "This type of strange looking creature swims in the sea"
This becomes: SLC → SS
All we know is that both animals swim in the sea. We can't draw the conclusion that one animal IS the other animal.
IF you had:
SLC → SS
-and-
SS → SF
THEN you could conclude that the "strange looking creature" is a "swordfish", because you would know that SLC → SS → SF.
But that's NOT what the argument says.
Let's use another example to make things more clear:
Premise 1: I go to work at the drugstore every Tuesday.
Premise 2: You always cover your Tuesday drugstore shift.
This can be diagrammed like this:
Me → DS on T
-and-
You → DS on T
Can you conclude that you and I are the same person?
What do I mean by this? Let's check out the diagrams for both statements.
Premise 1: "All swordfish swim in the sea"
This becomes: SF → SS
Premise 2: "This type of strange looking creature swims in the sea"
This becomes: SLC → SS
All we know is that both animals swim in the sea. We can't draw the conclusion that one animal IS the other animal.
IF you had:
SLC → SS
-and-
SS → SF
THEN you could conclude that the "strange looking creature" is a "swordfish", because you would know that SLC → SS → SF.
But that's NOT what the argument says.
Let's use another example to make things more clear:
Premise 1: I go to work at the drugstore every Tuesday.
Premise 2: You always cover your Tuesday drugstore shift.
This can be diagrammed like this:
Me → DS on T
-and-
You → DS on T
Can you conclude that you and I are the same person?
Posted: 11/04/2011 12:00
I understand from a logical point of view, I'm just confused in tens of language. "this" creature in the question seems to imply the creature being discussed... Namely, the swordfish. How do you know if the subject being referred to in the second premise is not the same subject referred to in the first premise with different vocabulary?
Posted: 11/04/2011 14:43
Jeremy,
Your question is valid. How do we know that the swordfish ISN'T a strange looking creature?
The answer is that we CANNOT determine that the swordfish is NOT a strange looking creature (based on the text in the passage--remember, we don't want to bring outside knowledge/opinions into our evaluation of the argument).
We know we cannot conclude that the swordfish is not a strange looking creature. But we also cannot conclude that the swordfish IS a strange looking creature.
So, based on the passage, "this strange looking creature" COULD be a "swordfish"--or it could be a totally different species. We have no idea. All we know is that they both swim in the sea. Therefore, the answer is "E".
Your question is valid. How do we know that the swordfish ISN'T a strange looking creature?
The answer is that we CANNOT determine that the swordfish is NOT a strange looking creature (based on the text in the passage--remember, we don't want to bring outside knowledge/opinions into our evaluation of the argument).
We know we cannot conclude that the swordfish is not a strange looking creature. But we also cannot conclude that the swordfish IS a strange looking creature.
So, based on the passage, "this strange looking creature" COULD be a "swordfish"--or it could be a totally different species. We have no idea. All we know is that they both swim in the sea. Therefore, the answer is "E".