"New Concepts" in the Conclusion - Explicitly *ask* whether you see any

KevinLuminateLSATKevinLuminateLSAT Monthly Member
in Logical Reasoning 611 karma

I was posting this as a comment to a thread in which someone asked for a "trick" to identifying assumptions. But I thought it'd be more useful as its own thread.

Unfortunately, there is no trick for answering assumption questions, and a full treatment of how to approach them isn't reasonable to fit in a forum post.

However, many, many students would benefit from adding another step in their process to NA questions (and SA, flaw, strengthen/weaken): ask whether there is a "new" concept in the conclusion.

This is because one of the most important aspects of identifying assumptions is noticing concepts in the conclusion that are not mentioned or logically covered in the reasoning. If there is a "new" concept in the conclusion, then the argument must be making some kind of assumption related to it. There may be other assumptions, too, related to gaps between premises, but you can be sure that at least one of the assumptions must be about that new concept in the conclusion.

As good LSAT students, you probably are already familiar with the idea described above. But a lot of people seem to rely mainly on passively noticing new concepts rather than actively thinking about this as a step in solving questions.

Let's work through some example that increase in difficulty.

Example 1:

Rooney graduated with the highest GPA in the history of our law school.
Thus, she must be good at writing law school exams.

Is there a new concept in the conclusion? Yes - do you see that "good at writing law school exams" is not mentioned in the premise? That means the author is making an assumption about the relationship between having the highest GPA and what that tells us about being good at writing law school exams. The author is assuming that having the highest GPA is an indicator of ability at law school exams.

Oftentimes students just fail to notice the difference between two concepts - they make the assumption that the argument itself is making, which is why it's hard to spot that assumption.

Example 2:

Our new neighbor, Xander, was convicted of over fifty murders and has been referred to by local historians as one of the worst serial killers in the United States.
So, we were living next to a murderer this whole time and never knew it!

Are there new concepts in the conclusion? You might see that the idea of "not knowing" our neighbor is a murderer is new - the evidence never provides anything related to what we knew about Xander. So the argument is assuming something about our lack of knowledge. What if we actually knew he was a killer before he was found out? Then the argument doesn't work.

Do you also see that the concept of "being a murderer" is also new? The evidence just refers to being "convicted" of murders and "being referred to by historians" as a serial killer. None of those is the same as being a murderer - what if he's an innocent person who was wrongly convicted and falsely thought of as a serial killer?

Another issue is that sometimes students don't realize something is a new concept because they think that the fact that it was mentioned elsewhere in the stimulus means that it's not new. But in reality, the concept can still be "new" if it's not mentioned in the reasoning that supports the conclusion.

In addition, you might have to translate the conclusion if it uses referential language. You can't identify new concepts in the conclusion unless you've spelled out exactly what the substance of the conclusion is.

Example 3:

Some social theorists claim that San Francisco's large homeless population could be reduced by implementing policies that condition the provision of free food and medical services to the homeless on their staying off drugs and actively looking for a job. However, most of the homeless do not react to incentives in the same way that the average non-homeless member of society would react.
Thus, the social theorists' claim is false.

If you break down the argument to premise and conclusion, here's what we get:

Premise: Most of the homeless do not react to incentives in the same way that the average non-homeless member of society would react.

Conclusion: SF's large homeless population cannot be reduced by conditioning the provision of free food/medical services to homeless on the requirement that they stay off drugs and actively look for a job.

Notice that the first sentence about the social theorists' claim is not a premise - it's simply referred to by the conclusion as being wrong. So in my understanding of the argument, the first sentence just disappears - we've translated that into the substance of the conclusion, and that first sentence has nothing to do with the reasoning of the argument. Now we can properly think about new concepts in the conclusion.

Do you see anything new? There are quite a few, so there are a lot of assumptions. But here are three that stand out to me.

  1. San Francisco's homeless? They weren't mentioned in the reasoning. Maybe they are different from the "most of the homeless" in the premise. The argument is assuming that San Francisco's homeless do not react to incentives in a significantly different way from "most" homeless. What if SF's homeless actually react more like the average non-homeless? That would undermine the argument by making the premise irrelevant. (Notice that if the premise said "All homeless..." then SF's homeless wouldn't technically be a "new concept" because they would be logically covered by the premise, even if the words "San Francisco" are new.)

  2. The whole idea of policies that condition food/medical services on requiring them to stay off drugs or look for a job --- where is that coming from? The premise doesn't say anything about them. The argument never explicitly identified these things as the kind of thing the premise was calling an "incentive". So the argument must be assuming that these kinds of policies relate to incentives and how people would react to them. It's assuming that having the conditions of staying drug free or getting a job would be things the average non-homeless would react to differently from most homeless. If this weren't true -- if the homeless and non-homeless reacted the same way to these conditions, then the premise would have nothing to do with the conclusion because they'd be talking about two different things.

  3. Reducing homeless populations? Does the premise say anything at all about reducing homeless populations or what is required for that? No. So the argument is making some kind of connection between the different reactions that homeless people have to incentives and the reduction of homeless populations. It's assuming that the policies in question - conditioning food/medical services on drug-free/look for job - can reduce homeless populations only if they work through incentivizing the homeless in some way. If there were some way that the policies could reduce homeless populations in a way that didn't relate to incentivizing them, then the premise (which was only about incentives), would have nothing to do with proving the conclusion. What if, for example, the policies could reduce homeless populations by stirring the moral fiber of SF's private citizens, who find the policies draconian and cruel and as a result band together to build thousands of free housing units for SF's homeless? The argument is assuming that this isn't a possibility.

I hope this helps if you're having trouble with assumptions and always find yourself thinking "there's no way I would have noticed that..." Maybe one reason you're not noticing it is because you're not explicitly identifying key concepts in the conclusion and asking whether they were mentioned or logically covered by the premises?

If you're reading quickly and uncritically, the difference between QOQOOQOQ and QOQOQOOQ might not stand out. But if you actually examine each set of letters and explicitly ask "Are these the same?" Then it's a lot easier to see where the difference is.


  • Matt SorrMatt Sorr Yearly Member
    1020 karma

    This is a great post! Thank you.

  • silobot1123silobot1123 Yearly Member
    32 karma

    This was actually really helpful. I am in the group of students that can see an assumption question and not understand the assumption I am missing because, I too, have made that assumption. I am definitely trying to get better. This was explained in a short and condensed way. Thank you!

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