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Hello All,

I quickly narrowed the possible answer choices down to B & D. I ultimately chose B after applying the negation test, but I am still confused as to how answer choice D is considered to be "out of scope".

By negating "B" we get the statement "some other gene in the flies....is required for the formation of the UV cells" and this negated version of the original statement completely undermines the argument by stating that the singular difference in cell composition is no longer enough to determine that that change leads to a lack of UV. Maybe some other cells are now required to determine whether or not a lack of UV occurs.

That much I understand.

However, doesn't AC "D" do something to a similar effect? By stating that the gene change had no effect on the flies other than UV, isn't that saying the same thing as "the gene change ONLY brings about the consequence of a lack of UV"? Doesn't this answer choice also eliminate alternative possibilities?

Is it incorrect because it does not satisfy the negation test? If we negate the statement we get "the gene change had some effect on the flies other than the lack of UV vision cells". I thought that this negated statement establishes that the gene change potentially had multiple effects on otherwise identical flies and thus undermined the connection between the premise and the conclusion.

My reasoning was: if the singular gene change had the potentiality to have multiple effects on the flies, wouldn't there be a case of causal over-determination, in which a single change in gene causes multiple events to occur. Thus making it almost impossible to accurately determine which event was actually caused. Or is the negated statement actually saying that a single change in the gene had the effect of a lack of UV IN ADDITION TO some other effects.

Sorry for the long post.

I'll answer this one. I hated this question too. Give me a second to type up a response.

Pro tip (not calling myself a pro, but I have heard this from some and it helps) #1: when you are doing assumption family questions really think about what the conclusion is saying by stressing the subjective words in your head (i.e. it MUST BE because of this, CLEARLY we get XYZ, etc.) If you stress those words that are really subjective and opinionated then it may help you out a bit. Why is this? I think its because LSAC likes to make their conclusions stronger to make the flaws easier to generate though I'm not particularly sure.

• Cloned flies have a changed gene but don't have UV vision
  +
  Other flies don't have the changed gene, but otherwise the same set of genes, yet have UV vision
  →
  Flies without UV vision must have some damage to the gene

Think about this. It must be the damage to this one gene? The scientists say, "Yep. There's nothing else. It's got to be that damage to that gene. Mhmm. Don't see anything else that could be wrong..." What is the assumption?! This should hit you in the face. The assumption is that there isn't something else that could have possibly eliminated the ability to have UV vision. Let's move on to the answer choices.

(A) It doesn't necessarily have to be well understood. Maybe they only know one thing about the relationship between genes and vision. Perhaps they know that genes affect vision. Okay. Does that mean that they are well understood? I don't think so. Eliminate.

(B) Okay this one sounds better. The argument does seem to be assuming that this one particular gene is really the only one responsible for the UV vision. However, maybe something else is the case. Maybe changing that one gene really had no affect on the vision directly but it was actually the case that changing that one gene causes a genetic mutation that changed another gene that changed the vision. Let's try the negation test that you did again...

• "There is some other gene in the flies in the experiment that is required for the formation of UV vision cells."

Oh this really hurts the argument. If there is another gene required then how can we say that the lack of UV vision cells is caused by the damage to this one single gene? Couldn't it be damage to something else?

(C) Definitely not necessary.

(D) This is a tempting answer. The best thing to do when you are stuck - as you know - is to negate it and think of a possible world in which the negation doesn't make the argument falter.

• The gene changed had some other effect on the flies other than the lack of UV cells

This doesn't sound as tempting as you probably though. There can be so many effects that the gene change had and they don't have to have anything to do with UV vision. Maybe the gene change caused the flies to fly slower? Maybe it suppressed their appetite? Who knows. Either way, there are definitely possible worlds in which this is negated and the argument doesn't fall apart. I don't know if I would go so far as to say this is out of scope - I would probably just say it isn't necessary. Although, one could argue that this is out of scope because we don't care about other effects. We are just talking about one effect - the vision.

(E) Not necessary at all.

akechi wrote: However, doesn't AC "D" do something to a similar effect? By stating that the gene change had no effect on the flies other than UV, isn't that saying the same thing as "the gene change ONLY brings about the consequence of a lack of UV"? Doesn't this answer choice also eliminate alternative possibilities?

Is it incorrect because it does not satisfy the negation test? If we negate the statement we get "the gene change had some effect on the flies other than the lack of UV vision cells". I thought that this negated statement establishes that the gene change potentially had multiple effects on otherwise identical flies and thus undermined the connection between the premise and the conclusion.

My reasoning was: if the singular gene change had the potentiality to have multiple effects on the flies, wouldn't there be a case of causal over-determination, in which a single change in gene causes multiple events to occur. Thus making it almost impossible to accurately determine which event was actually caused. Or is the negated statement actually saying that a single change in the gene had the effect of a lack of UV IN ADDITION TO some other effects.

I'll be perfectly honest, I had to go look up what "causal overdetermination" meant. According to wikipedia "Overdetermination is a phenomenon whereby a single observed effect is determined by multiple causes at once, any one of which alone might be enough to account for ("determine") the effect."

So, that seems to be fundamentally different than the situation you're talking about. In true causal overdetermination, multiple causes all cause the same effect, thus, when the effect appears, you don't know which cause is to blame. But in this scenario (with negated (D)), we would have a single cause, and multiple effects.

If the sun shining causes me to be happy, dance a little dance, and sing a little song, it's not at all difficult to tell which effect will occur - they all will!

So, if the gene change causes the flies to dance and sing, who cares?! We still know that they have no UV vision.

Now, if you are interpreting the negation to be something like "The gene change might cause any number of effects, but it may not cause all of them at once", then you are suggesting that all of those cause-effect relationships are just "maybes". That's not okay. Saying something has multiple effects is not the same thing as saying that a thing has multiple things it could possibly cause but maybe not.

You're trying to force the negation of (D) to a place where it creates the idea that maybe the gene change doesn't cause the loss of UV sight. But that's not what the answer (or it's negation) are about - they are about whether or not there are other effects also.

• Original statement: Changed gene has no other effects, aside from killing UV sight.
  Negation:Changed gene has some other effect, aside from killing UV sight.

Thoughts?

akechi wrote: However, doesn't AC "D" do something to a similar effect? By stating that the gene change had no effect on the flies other than UV, isn't that saying the same thing as "the gene change ONLY brings about the consequence of a lack of UV"? Doesn't this answer choice also eliminate alternative possibilities?

Also, in regards to the bolded, I also wanted to point out that many incorrect answer choices will eliminate some possibilities - technically, anything with definitive language would eliminate something. However, the question is really 'do those eliminated possibilities actually affect my conclusion?'

Since the conclusion is trying to claim a definitive (single) cause for lack of UV sight, eliminating another possible cause for the lack of UV sight directly undermines that. Eliminating other possible effects of that same cause doesn't carry the same punch, since it doesn't make it any less likely that the proposed cause is in fact the cause.

It's not a red flag for an answer choice to simply eliminate some possibilities; it needs to eliminate some possibilities could destroy or compete with the conclusion if true.

Hi WaltGrace,

Thank you for the detailed response! After evaluating the core + the logic of the argument, I am seeing much more clearly how AC "B" is truly the best AC.

However, there were some snippets of information in your response that I wish to get some clarification on. You posed this interesting idea about what the negation test is trying to accomplish. In the negated version of AC "D" you say that "..there are definitely possible worlds in which this is negated and the argument doesn't fall apart." Do you mean to say that, in order to fulfill the requirements of the negation test, the negated answer must hold across all possible worlds? I've never thought about it this way. It makes complete sense though, considering that we our task in Necessary Assumption questions is to find an assumption that is necessarily true.

Also, I realized that there was a major distinction to be made between AC "B" & "D". It seems like in "B" the idea that is being discussed within the statement are the circumstances surrounding the cause of UV vision. Whereas in "D" the idea under discussion is the possible effects of the changes in genes. Am I looking too far into this question and the differences between these two answer choices? Or is there some lesson to be learned about the concept of causality and the characteristics of incorrect answer choices in Assumption family questions.

If anyone can chime it, I would be forever thankful!

akechi wrote:Hi WaltGrace,

Thank you for the detailed response! After evaluating the core + the logic of the argument, I am seeing much more clearly how AC "B" is truly the best AC.

However, there were some snippets of information in your response that I wish to get some clarification on. You posed this interesting idea about what the negation test is trying to accomplish. In the negated version of AC "D" you say that "..there are definitely possible worlds in which this is negated and the argument doesn't fall apart." Do you mean to say that, in order to fulfill the requirements of the negation test, the negated answer must hold across all possible worlds? I've never thought about it this way. It makes complete sense though, considering that we our task in Necessary Assumption questions is to find an assumption that is necessarily true.

Also, I realized that there was a major distinction to be made between AC "B" & "D". It seems like in "B" the idea that is being discussed within the statement are the circumstances surrounding the cause of UV vision. Whereas in "D" the idea under discussion is the possible effects of the changes in genes. Am I looking too far into this question and the differences between these two answer choices? Or is there some lesson to be learned about the concept of causality and the characteristics of incorrect answer choices in Assumption family questions.

If anyone can chime it, I would be forever thankful!

Christine would probably provide a better answer than I would (*nudge* *nudge*) yet that is basically what I am saying. When you get a vague negation such as the one posited in (D), i.e. that there may be "some" other effects," then you can think of crazy situations. The crazier, sometimes the better! Why is this the case? Because the negation doesn't specify exactly what the "some" is. It could be anything! If you do find a way in which the negation can happen and the argument doesn't fall apart then the answer choice isn't necessary.

Something that is truly necessary is necessary in ALL cases. You see what I mean? If it is not necessary in all situations that the argument can possible be discussing, it was never really necessary in the first place.

I'll be perfectly honest, I had to go look up what "causal overdetermination" meant. According to wikipedia "Overdetermination is a phenomenon whereby a single observed effect is determined by multiple causes at once, any one of which alone might be enough to account for ("determine") the effect."

So, that seems to be fundamentally different than the situation you're talking about. In true causal overdetermination, multiple causes all cause the same effect, thus, when the effect appears, you don't know which cause is to blame. But in this scenario (with negated (D)), we would have a single cause, and multiple effects.

If the sun shining causes me to be happy, dance a little dance, and sing a little song, it's not at all difficult to tell which effect will occur - they all will!

So, if the gene change causes the flies to dance and sing, who cares?! We still know that they have no UV vision.

Now, if you are interpreting the negation to be something like "The gene change might cause any number of effects, but it may not cause all of them at once", then you are suggesting that all of those cause-effect relationships are just "maybes". That's not okay. Saying something has multiple effects is not the same thing as saying that a thing has multiple things it could possibly cause but maybe not.

You're trying to force the negation of (D) to a place where it creates the idea that maybe the gene change doesn't cause the loss of UV sight. But that's not what the answer (or it's negation) are about - they are about whether or not there are other effects also.

• Original statement: Changed gene has no other effects, aside from killing UV sight.
  Negation:Changed gene has some other effect, aside from killing UV sight.

Thoughts?

[/quote]

Hi Christine!

I had just finished typing up a response to clarify some confusions, but my internet gave out . So here it is again.

Thank you for trying to help a foolish student out. This is embarrassing. I guess I meant to say "causal underdeterminiation". By which I mean: a singular cause has so many effects, that it could become hard or almost impossible to determine which events actually align in a causal relation. The negated version of the statement in "D" allows us to become fairly creative with crafting possibilities, so couldn't we say that the "some" other possible effects are actually infinite in number so as to make the causal link between the gene changes and its infinite amount of effects rather obscure or pointless?

What I was hoping to establish by taking it to this extreme is to show that the negated version of "D" actually destroys the assumed causal link between gene change and lack of UV vision, thereby undermining the link between premise and conclusion. If we no longer know that there exists a causal link between the singular gene change and the lacking of UV, doesn't the argument fall apart?

What I hope to get out of this question is a better understanding of the concept of causality within the LSAT world. I am sorry if any of this is coming off as argumentative or being difficult for the sake of being difficult. But, right now, I am honestly confused as to why my analysis of AC "D" is incorrect and where exactly I went wrong in my analysis.

Ahh, I see Christine. Correct me if I am wrong, but you are saying the term "has" definitively states that ALL of the effects of the cause MUST occur whenever the cause is present. So, if we were to interpret the negated statement to say that a singular cause has multiple effects, which may or may not occur all at the same time, our analysis would be fundamentally incorrect.

But, sorry for pushing this point again, even if we were to take on the former interpretation of all effects definitely occurring, wouldn't the possibility of infinite effects still present a problem?

WaltGrace83 wrote:

akechi wrote:Hi WaltGrace,

Thank you for the detailed response! After evaluating the core + the logic of the argument, I am seeing much more clearly how AC "B" is truly the best AC.

However, there were some snippets of information in your response that I wish to get some clarification on. You posed this interesting idea about what the negation test is trying to accomplish. In the negated version of AC "D" you say that "..there are definitely possible worlds in which this is negated and the argument doesn't fall apart." Do you mean to say that, in order to fulfill the requirements of the negation test, the negated answer must hold across all possible worlds? I've never thought about it this way. It makes complete sense though, considering that we our task in Necessary Assumption questions is to find an assumption that is necessarily true.

Also, I realized that there was a major distinction to be made between AC "B" & "D". It seems like in "B" the idea that is being discussed within the statement are the circumstances surrounding the cause of UV vision. Whereas in "D" the idea under discussion is the possible effects of the changes in genes. Am I looking too far into this question and the differences between these two answer choices? Or is there some lesson to be learned about the concept of causality and the characteristics of incorrect answer choices in Assumption family questions.

If anyone can chime it, I would be forever thankful!

Christine would probably provide a better answer than I would (*nudge* *nudge*) yet that is basically what I am saying. When you get a vague negation such as the one posited in (D), i.e. that there may be "some" other effects," then you can think of crazy situations. The crazier, sometimes the better! Why is this the case? Because the negation doesn't specify exactly what the "some" is. It could be anything! If you do find a way in which the negation can happen and the argument doesn't fall apart then the answer choice isn't necessary.

Something that is truly necessary is necessary in ALL cases. You see what I mean? If it is not necessary in all situations that the argument can possible be discussing, it was never really necessary in the first place.

Sorry WaltGrace, you know I love you, but I have to disagree with you on this one. A negated necessary assumption does not have to destroy the conclusion in every universe - it merely has to destroy it in some universes. An *incorrect answer* negated will destroy the conclusion in zero universes, unless you start adding in new information.

Let's take one of my favorite silly arguments:

• PREMISE: All boys like sports
  CONCLUSION: Andy like sports

One thing we are assuming is that Andy is a boy. The negation of that is that Andy is not a boy. If Andy is a girl, the argument dies - but note that this does not mean that the conclusion will always be false!

It's possible that girl-Andy likes sports! In the universe where girl-Andy likes sports, this conclusion is then factually correct, but the argument is still invalid. We cannot conclude from the premise that All boys like sports that girl Andy must like sports - because we must consider the universe where girl-Andy does not like sports.

In other words, once we negate the conclusion, the existence of one universe that destroys the conclusion is enough to know that the argument is destroyed (in all universes). The conclusion is no longer concludable!

Think of it this way: the conclusion needs to be true all.the.time., in order for it to be valid right? What's the negation of 'all the time'? How can we be the snot nosed kid saying NUH UHHHHHH to the conclusion? We don't need to say that the conclusion is never true - we just need to say 'nuuuh uhh, conclusion, not always -- see, I found a universe where it isn't true!'.

In this situation, if we load up the gene change with other potential effects, that never kills the conclusion - not in any universe ever. Not unless you start adding in other information. And the negation of the correct answer choice doesn't kill the conclusion in every universe - if other genes are required for UV sight, that doesn't mean our conclusion is always bad - it just opens up the clear possibility that it is false.

Essentially: Negated assumptions do no necessarily make conclusions false all the time. They only have to make them false in some potential universes, and by doing so, they destroy the argument (i.e., destroy the connection between the premise and the conclusion).

akechi wrote:Ahh, I see Christine. Correct me if I am wrong, but you are saying the term "has" definitively states that ALL of the effects of the cause MUST occur whenever the cause is present. So, if we were to interpret the negated statement to say that a singular cause has multiple effects, which may or may not occur all at the same time, our analysis would be fundamentally incorrect.

But, sorry for pushing this point again, even if we were to take on the former interpretation of all effects definitely occurring, wouldn't the possibility of infinite effects still present a problem?

It's an interesting issue that you raise, but I don't see why it would.

I think you're hung up on the idea that one cause having lots of effects somehow unhooks the causality altogether, and I just don't think that's true. We could load up the gene change with millions and millions of effects, and that wouldn't remove the causal relationship between the gene change and just one of the effects.

The reason why causal overdetermination is a problem is because any one of the causes could be the culprit, and we don't know which one. When a cause has multiple effects, those effects don't change anything about the other cause-effect relationships. The sun shining could cause me to sing, dance, play the fiddle, bake a cake, scream at the top of my lungs, and a million other things. But none of that changes the fact that the sun shining causes me to sing. Each cause-effect pair is still a true and valid statement - no matter how many of them there are.

(BTW, not to nitpick, but "underdetermination" is actually when we don't have *enough* causal factors for an effect to present. I only point this out because using those terms may cause you to think that single-cause: multiple-effects is a recognized and categorized problem or error, when it actually isn't.)

I think I may have communicated ineffectively. Let me rephrase.

• "The gene change had SOME effect on the flies other than the lack of ultraviolet vision cells" is the negation of (D).

What I am saying is that if we think of one instance in which the negation of (D) happens, and the argument still has the possibility to follow the premises, then it is not necessary to the argument. Perhaps the gene change had some effect. Maybe it just effected the ability for the fly to fly around. Does this hurt the argument? Not really, no. It could still be that the species lacking UV vision must mean it has damage to the altered gene.

However, I guess what you were really talking about was the opposite, that which is necessary for the argument. If we negate a correct answer, something like the following happens:

• "Some other gene in the flies in the experiment is required for the UV cells to form" - negation of (B)

Given only the information that we have in the stimulus, we simply cannot conclude that the conclusion is true.

• Cloned flies have a changed gene but don't have UV vision
  +
  Other flies don't have the changed gene, but otherwise the same set of genes, yet have UV vision
  +
  Some other gene in the flies in the experiment is required for the UV cells to form
  →
  Flies without UV vision must have some damage to the gene

If we take all those premises, including the negated correct answer, how can we just say that it was because of the damage to the gene that the flies didn't have UV vision? The negated assumption brings us to seriously doubt our conclusion. It weakens it. It makes it so that - without any other information - we cannot really conclude our conclusion.

EDIT: I think I see where I misspoke. I guess what I meant to say is that you can absolutely bring in any universe when you think about those vague words like "some" in regards to "effect." What is the effect I ask? I could make up any "effect" that I want and if it is true that the argument could still follow with something that I made up, then it is not necessary.

Okie Dokie!

It all makes perfect sense now. Also, thank you for clearing up that mistake between overdetermination and underdetermination. Further thanks for delving so deeply into what the negation test is really trying to accomplish. The subtlety of the LSAT never ceases to amaze me.

So essentially, the negated version of the correct answer choice makes the logical form of the argument invalid. And validity in logic can be defined as the conclusion being logically entailed by its premises. Or to word it more strongly, if the premises are true, then the conclusion is NECESSARILY true (i.e. soundness). So in the case of your favorite example:
Premise: All boys like sports
Conclusion: Andy likes sports

A necessary assumption would be Andy is a boy. Inserting that assumption into the argument would make the conclusion necessarily follow - and thus a valid argumentative form. And the negated version of the statement Andy is NOT a boy (e.g. post-op trans, female, etc.) would provide a case in which the conclusion does NOT necessarily follow, thereby showing it to be invalid, and thus proving that the original non-negated version is indeed necessary.

But, if the crux of the matter is finding a necessary assumption that makes the argument form valid, then why are we at all concerned with the factual matters of the argument?

"It's possible that girl-Andy likes sports! In the universe where girl-Andy likes sports, this conclusion is then factually correct, but the argument is still invalid. We cannot conclude from the premise that All boys like sports that girl Andy must like sports - because we must consider the universe where girl-Andy does not like sports.

In other words, once we negate the conclusion, the existence of one universe that destroys the conclusion is enough to know that the argument is destroyed (in all universes). The conclusion is no longer concludable! "

Your discussion of factual correctness just threw me off. I thought within the LSAT, we were completely unconcerned about whether or not an argument is sound. All we are supposed to care about is the validity of the argument forms.

akechi wrote:Okie Dokie!

It all makes perfect sense now. Also, thank you for clearing up that mistake between overdetermination and underdetermination. Further thanks for delving so deeply into what the negation test is really trying to accomplish. The subtlety of the LSAT never ceases to amaze me.

So essentially, the negated version of the correct answer choice makes the logical form of the argument invalid. And validity in logic can be defined as the conclusion being logically entailed by its premises. Or to word it more strongly, if the premises are true, then the conclusion is NECESSARILY true (i.e. soundness). So in the case of your favorite example:
Premise: All boys like sports
Conclusion: Andy likes sports

A necessary assumption would be Andy is a boy. Inserting that assumption into the argument would make the conclusion necessarily follow - and thus a valid argumentative form. And the negated version of the statement Andy is NOT a boy (e.g. post-op trans, female, etc.) would provide a case in which the conclusion does NOT necessarily follow, thereby showing it to be invalid, and thus proving that the original non-negated version is indeed necessary.

But, if the crux of the matter is finding a necessary assumption that makes the argument form valid, then why are we at all concerned with the factual matters of the argument?

"It's possible that girl-Andy likes sports! In the universe where girl-Andy likes sports, this conclusion is then factually correct, but the argument is still invalid. We cannot conclude from the premise that All boys like sports that girl Andy must like sports - because we must consider the universe where girl-Andy does not like sports.

In other words, once we negate the conclusion, the existence of one universe that destroys the conclusion is enough to know that the argument is destroyed (in all universes). The conclusion is no longer concludable! "

Your discussion of factual correctness just threw me off. I thought within the LSAT, we were completely unconcerned about whether or not an argument is sound. All we are supposed to care about is the validity of the argument forms.

I think Christine was just making a point about how I threw around the word "any" too hastily. The LSAT is not about logical soundness. The valid argument on the LSAT could be "mammals all have one leg. Humans are mammals. Therefore, humans have one leg."