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Skylar January 14, 2020

@mprezzy, happy to help.

You are correct. The word "some" is defined as "at least one, possibly all."

With this definition, we can change an S->N statement into a some statement as follows:
A -> B
B - some - A (assuming that A exists)

However, we cannot change a some statement into an S->N statement. This is because we do not know that the "some" used in the original statement means "all." If it doesn't mean all and instead only refers to a portion of something, it cannot be accurately written as an S->N statement.

Does that make sense? Please let us know if you have any other questions!

mprezzy January 18, 2020

Could you be so kind to provide a visual example of both: 1. A statement that doesn't mean all and 2. A statement that is referring to a portion? Maybe it will be easier for me to understand the difference if I see it visually.

mprezzy January 18, 2020

I actually just found an example that I do not understand since we have determined in the previous threads that some cannot become all.

P: D -some- X
X -some- D

P: Missing

C: not A -some- X
X - some - not A

We are not starting the combination with not A because A is not there so:

D - some - X -some - not A
D - some - not A

Conclusion:

D -> not A
A -> not D

How did "some" become "all"?

Skylar January 19, 2020

@mprezzy, let me see if I can help to clarify.

A some statement that does not mean all and a some statement that refers to a portion of something would be the same things.

Let's say I have ten markers, all of which are blue. In this case, I could say "all of the markers are blue" or "some of the markers are blue," and both statements would be true. Now, let's say that five of my ten markers are blue and the other five are red. I could say "some of the markers are blue," but I could not say that "all of the markers are blue." Does that make sense? If you can start by saying that you have all, then you can safely conclude that you have some. However, if you can only start by saying that you have some, you cannot necessarily say that you have all.

The example that you have provided does not work here because it is a Missing Premise Question. In these types of questions, we can create our own a statement to fill the gap as needed. We are able to create an S->N statement to fill the gap here because the question is specifically calling for it. This is different from the question attached to this thread, which asks what "must be true."

Does that help?

mprezzy January 19, 2020

That does help. Thank you! Sorry to split hairs but I have another question for further clarification: two "all" statements that share the same necessary conditions do or do not make a some statement? For example:

A->D
C->D

Can I say that A->D
and it's final form would be:
C-some-A?

Brett-Lindsay July 18, 2020

Hi @mprezzy,

I think that you can only combine two "all" statements when they share a common sufficient condition, not a necessary condition. We could first take the contrapositives and combine those:
not D --> not A
not D --> not C
therefore,
not A --some-- not C

We can combine them like this because we could turn an "all" statement into a "some" statement, and then combine the "some" with the "all":

not D --> not A becomes
not A --some-- not D

Combined, we get:
not A --some-- not D --> not C
not A --some-- not C

shunhe July 27, 2020

Hi @mprezzy,

Thanks for the question! You can’t really say that because all As are Ds, and all Cs are Ds, that some Cs are As. And let’s think about a common example. All tomatoes are fruits. Also, all avocados are fruits. But are some avocados tomatoes, or some tomatoes avocados? No, not at all. So we can’t go from

A—>D
C—>D

to C <—some—> A.

Hope this helps! Feel free to ask any other questions that you might have.