on main conclusion questions, some answer choices use referential phrasing of the premise in the answer choices. is it true that the ones with the referential phrase of the main premise (instead of the minor premises) is the correct one? #help

What I think they are trying to highlight with that section is the fact that if you confuse sufficiency for necessity then you can validate an argument that was originally invalid.

The first argument is:

All birds migrate south in winter. The monarch butterfly is not a bird. Therefore, the monarch butterfly does not migrate south in winter.

Lawgic with assigned meanings (correct me if I'm wrong I'm also learning):

Lawgic: Birds---> Migrate South

CP: /Migrate South --> /Not Birds

CP English: If they don't migrate south in the winter, they are not a birds. This is not the same thing as "the monarch butterfly does not migrate south in the winter," which is why it's an invalid argument as presented above in bold

More explained:

Why it's invalid: We know all birds migrate south, but we don't know if butterflies also migrate (the argument doesn't say). All the argument tells us is that a butterfly is not a bird. However, that's not enough evidence to come to the valid conclusion that butterflies don't migrate south. We just don't have enough evidence to reasonably conclude that statement, so we can't say if it's true or false.

However your question is why the following argument is valid:

Only birds migrate south in winter. The monarch butterfly is not a bird. Therefore, the monarch butterfly does not migrate south in winter.

Migrate South--> Birds

CP: /Birds---> /Migrate South

CP English: If it's not a bird, then it does not migrate south in the winter.

This is the important part! The statement we are given says "The monarch butterfly is not a bird" The Counterpostive says "If it's not a bird, then it does not migrate south in the winter." Because the OG statement and the CP are equivalent, then we can say the conclusion "Therefore, the monarch butterfly does not migrate south in winter." This makes the second statement, the one you commented on valid. *It's valid because we confused sufficient for necessary. The issue with that is when we confuse sufficient and necessary we can change what the argument's purpose is, we can change one word by misinterpreting sufficient and necessary and convince ourselves that the statement is valid when it's invalid.

Hope that helps!

I think about it like this: If your in Grif it's necessary that you are brave. If your brave it is NOT necessary than you are in Gryffindor.

The example given in the above lesson is noted as invalid (because you can be brave and still be in another house) which is why the lawgic B==> Grif is invalid

I was in the same place in my understanding, not even 2 weeks ago. It's very wordy in the beginning and if you don't take breaks it can get jumbled, at least it did for me. I hope this helps

Lawgic: I think it would be Grif --> Brave and the contrapositive would be /Brave --> /Grif.

English: We know that if you're in Grif then you are brave. Thus if you are not brave, then you are not in Grif.

I spent hours on the difference between sufficient and necessary when I learned the difference between "only if" and "if" during the foundations section. I found the lessons on Indicators a good way to explain the difference between what is sufficient and necessary. It's easy to see what's logically valid if we know what arguments that are sufficient and that are necessary, look like. (Foundations> Conditional and Set Logic > Group 1 Sufficient Conditional Indicators:New York Example (& Group 2 Necessary Conditional Indicators:Citated as Late Example))

I thought the same thing, but I think some of these might be necessary for the logical reasoning portions and since there is going to be multiple LR sections, it might be helpful to understand the formal arguments in lawgic terms. #help

I think it's because if you follow the curriculum along, we haven't learned how to apply the both option to Lawgic yet. #help

I am going to become fluent in lawgic if it's the last thing I do

#help What would be the significance of differentiating between background knowledge, context, and concession? We know that premise and conclusion have a big difference that's important to understand how to answer questions but what about concession, what is the importance?

#help I'm just wondering how knowing the difference between major and minor premises, will help on the test. I understand how identifying the sub-conclusion is helpful because it helps clear out any confusion between premise and conclusion. I'm still unsure about the significance of major and minor premises when it comes to the test.

I am wondering the same thing

I thought the Trash Bin Argument would be in the middle in terms of strength, because I was looking at solely how long they were in relation to each other. I realized that the trash bin argument isn't as strong because the link between the premise making the conclusion most likely true is weaker than the other 2 arguments which is why it's on the weakest side and not between Disney and Tiger