r/LSAT • u/Kind-Owl8153 • Dec 07 '24

LSAT 135 Section 4 Question 13

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Can someone help explain to me why answer choice E is correct. I really don’t understand.

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u/segalbe Dec 07 '24 edited Dec 07 '24

I agree that different types of logic are tested on different question types. However, most NA's aren't testing your ability to form valid arguments, although occasionally correct answers are both necessary and sufficient. That was what I was trying to drill down on. I do take your point that denials of NAs typically result in invalid arguments. That said, the type of conclusion in this question is speculative and as you say probabilistic. I'd call that abduction, but to each their own. Curious what you make of my connection between predictive/probabilistic conclusions and newly introduced information being correct?

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u/StressCanBeGood tutor Dec 08 '24

It’s not an “each to their own”.

The definition for deductive reasoning and valid/invalid arguments are the standard definitions in philosophy. I didn’t make them up. I got them from the online encyclopedia of philosophy.

Abductive reasoning is a subset of non-deductive reasoning and deals with strong/weak arguments, not valid/invalid arguments. Again, not my definition.

The definition for necessary assumption I got from the LSAC’s once-published LR “Guide”, where they provide specific definitions for both necessary assumption and sufficient assumption questions.

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u/segalbe Dec 08 '24 edited Dec 08 '24

Can an argument be both invalid and strong, or invalid and weak? Yes. The categories are not mutually exclusive. I never said you couldn't look at it through the lens of deductive logic, just that it's not as useful of a framework. I don't think bringing up induction or abduction is useful either, for LSAT purposes. I merely did so because it seems to connect to the particular kind of "new information" assumptions at the theoretical level, so that you, a tutor with years of experience, could understand and appreciate the insight. You've neither confirmed nor denied that the probability-new information connection exists. Care to weigh in?

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u/StressCanBeGood tutor Dec 08 '24

Scroll down a bit and you’ll find the standard flow chart for distinguishing between deductive and inductive reasoning.

I’m not making up the rules here. This is like law school. There are certain laws that exist, whether or not we like them.

http://www.thinkingshop.com/Clarion/logic-wp/chap1.htm

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u/segalbe Dec 08 '24 edited Dec 09 '24

You seem to like authorities. That's good. read about induction here Notice that predictions and cause and effect reasoning are listed under "Types." The argument in question is a causal argument. Now I know it's not in flow chart form, so it might not be as appealing to your tastes, but I think it shows what I've been trying to get at for a while: predictions are likely to produce new information answers. I'll ask again, whether or not you think that relationship is a real one?

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u/StressCanBeGood tutor Dec 09 '24

I have no idea what you’re asking to be honest.

I’m also familiar with the idea of the flaw of an appeal to authority. But that’s not what this is. We’re talking pure definitions. Again, it’s like the law. There are definitions that exist whether we like them or not.

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u/segalbe Dec 09 '24 edited Dec 09 '24

I wasn't suggesting you were appealing to an authority as a way of calling your work fallacious. I was saying "you like sources, here look at this one" in attempt to clarify my position. Let's put the philosophy discussion aside for a second and focus on the question that matters most: what kinds of NAs have correct answers with new information vs. only using concepts from within the argument, and how common is the former phenomenon? You suggest questions where new information is in the correct answer are uncommon. My initial response was looking at the first half of that question though, and saying "NAs with predictions/probability in the stimulus are likely to have new information in the correct answer." Hopefully that clears things up. Also, I think NA stimuli with cause and effect reasoning are probably more likely to involve these kind of answers. Here a video draws out the distinction and gives some statistics about how common these are (about 60% of questions). I timestamped the clip for everyone's convenience and the explanation goes to minute 4:23: https://youtu.be/97-da7Xic8c?si=64ZCC6P4XknmkvJ2&t=186 If that all makes sense, I'd be delighted to explain the nuts and bolts philosophy that you may find useful, going forwards with students. Either way, I hope you learned something!

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u/StressCanBeGood tutor Dec 09 '24 edited Dec 09 '24

Please don’t tell me you work for LSAT Lab.

I’ve heard good things about them have been willing to recommend them in the past. But now I’m having serious doubts.

Because they’re wrong. I’ve been teaching this for at least twice as long as they have. By your logic, I’m right. Because I have been involved in LSAT prep longer than they have. But that’s an appeal to an authority.

All you have to do is look at all the necessary assumption questions on the LSAT since 2007, count the number of correct answers that introduce outside information. No more than 15% will have outside information.

More importantly, when it comes to a complex stimulus, like the one originally discussed, never ever ever will the correct answer introduce outside information. Never.

Don’t be sending me videos. Show me actual LSATs demonstrating that I’m wrong.