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Still however, I fail to see how this is a necessary assumption. If this assumption were false, then the conclusion of the argument could very plausibly remain true. The support of the premises for the conclusion, however, falls away.

That's what I was getting at in my previous explanation. If the assumption is negated (i.e. the decline of the female population is not proportional to that of the general population), it can either support (as you explained in the OP) or weaken (as I explained earlier) the argument. It is true that the conclusion remains plausibly true; but the negated assumption implies that the argument is not 100% true (valid), because it can both strengthen and weaken the argument. Because the negated assumption shows that the argument is not 100% true, it is a necessary assumption.

Which I suppose brings me back to my original question: does the negation of a necessary assumption guarantee invalidly of the conclusion or only the way it is being argued?

The task in NA question is not to utterly cripple the given argument. All you have to do by negating a necessary assumption is to show that the argument is not 100% true.

Now I understand. Thank you for your help!

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You arent disputing the truth or falsity of the conclusion or premises in any LR question.

In NA questions, you are drawing a link between the premises and conclusion. Your only task in NA questions is to make the premises remotely relevant to the conclusion.

If I say "I like to go to the beach" and, in response you say "oh you would like it in Guadelestan." What is the necessary assumption? There is some beach-like thing in Guadelestan. There is something remotely similar to a beach in Guadelestan. Obviously, I could like it in Guadelestan if there wasnt a beach, there's probably a lot of things i like other than beaches that could be in Guadelestan. As in, yes there are possible worlds where the conclusion is true even though my NA is not. But, based on what I said about liking beaches, we need to draw some link of relevancy, in order for my statement about liking the beach to be remotely relevant to the conclusion that I would like G.

Again, go back over the NA section of the CC. You couldve spent this time watching the intro to NA videos again.

Thank you.

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I'm gonna let you figure it out by saying this:

The human species is in danger when at least 2/3 of the population dies.

2/3 of people with blue hair have died.

Thus, the human population is in danger.

The necessary assumption here is just that the # of blue haired people dying is representative of how many people in the entire population are dying.

Otherwise, who cares that a portion of a portion of the population died. We have no reason to fear for the future of the human race if blue haired people's deaths are outliers.

Thank you for your response, but is that really a necessary assumption? If the percentage of blue eyed people dying is less than the percentage of people dying, you're necessary assumption would be false but the conclusion would still be true.

How do you keep getting to "less than"? What do you mean my necessary assumption is "false"? I presented to you an argument, which you assume to be true. If true, what is the necessary assumption? You arent supposed to be attacking the premises.

"If the percentage of blue eyed people dying is less than the percentage of people dying..." then the argument falls apart. Your statement makes it apparent that my assumption is NECESSARY.

In NA questions, you arent disputing the accuracy of the NA. If you negate my statement, it is not the case that 2/3 of blue haired people are representative of the population, then the argument falls apart.

The only possible way that we can conclude that the entire human population is in danger, is if 2/3 of the human population is dead. We're presented with a random statement about 2/3 of blue haired people dying, and then concluding that the human population is in danger. What must be the case here?

Go back over the beginning of the NA section in the CC bc I think your approach is off.

Thank you for your response. I think we are getting to the crux of the issue, but I think you are misunderstanding me slightly. I am not debating the truth of your NA, I am concerned about the truth of the conclusion. If your necessary assumption is negated, yes, your argument falls apart, but the conclusion itself remains entirely plausible. Am I understanding correctly then, that when we talk about a necessary assumption, we are saying that it is necessary to the validity of the argument, not the truth/validity of the conclusion? Thank you for your thoughtful help!

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My thought is that this is not a necessary assumption as the argument's conclusion could still be valid if the general population was declining MORE than the nesting female population (which would mean the decline was not proportional).

That's true. But it can also go the other way: What if the decline of the general population was less than that of the nesting female population? That would make the decline disproportional but weaken the argument at the same time. The decline's being disproportional thus shows the argument is invalid (not 100% true). Therefore, (A) indeed is a necessary assumption. Granted, (A) is worded a little stronger than an ideal NA answer, but (thankfully) it's the only one bridging the gap between the female and the general populations.

This also made me wonder whether a necessary assumption relates to the argument or conclusion... is an assumption necessary if its falsehood destroys the argument but still allows for the possibility of the truth of the conclusion?

An argument by definition includes a conclusion so, technically speaking, whatever relates to the conclusion relates to the argument as well. But most of the time, a necessary assumption relates to the conclusion. I say most because I seem to recall a Flawed Assumption question, which involved bridging a gap between two premises without addressing the conclusion.

That really depends on the question.

Thank you for your response. To answer your question, if the general population was declining less than the nesting female population was declining then the argument's conclusion of there being a clear danger of extinction would be false. That is why this is a sufficient assumption (as J.Y. says in the video). Still however, I fail to see how this is a necessary assumption. If this assumption were false, then the conclusion of the argument could very plausibly remain true. The support of the premises for the conclusion, however, falls away. Which I suppose brings me back to my original question: does the negation of a necessary assumption guarantee invalidly of the conclusion or only the way it is being argued? I am not trying to be difficult, rather my underlying question still remains. Thank you again for your help.

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FYI, there's a forum rule against quoting directly from PTs.

Thank you. I was unaware of this rule. I have since edited the post to paraphrase the test. Thank you again.

@ said:

I'm gonna let you figure it out by saying this:

The human species is in danger when at least 2/3 of the population dies.

2/3 of people with blue hair have died.

Thus, the human population is in danger.

The necessary assumption here is just that the # of blue haired people dying is representative of how many people in the entire population are dying.

Otherwise, who cares that a portion of a portion of the population died. We have no reason to fear for the future of the human race if blue haired people's deaths are outliers.

Thank you for your response, but is that really a necessary assumption? If the percentage of blue eyed people dying is less than the percentage of people dying, you're necessary assumption would be false but the conclusion would still be true.

Thank you for your response, but why do the words "less likely" make the correct answer a necessary assumption?