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Assumptions
WHAT ARE ASSUMPTIONS?
Simply put, they are premises that the author has left out of the argument. That is all assumptions are, period. Let’s consider our previous argument:
Premise 1:
The state of Qari is hostile to our national interests.
Premise 2:
The state of Qari harbors many rare and desired natural resources.
Conclusion:
Therefore, we should invade and occupy the State of Qari.
What are some assumptions? In other words, what are some premises – statements that would support the conclusion – that the author has left out? How about: Invaders of a country often gain access to the country’s natural resources. Do you think that statement is an assumption? We can find out. If it is an assumption, then by definition, it’s a premise that the author has left out. That means if we add it into the argument, it would do what all premises do: support the conclusion. Let’s add that statement in and see what happens.
Premise 1:
The state of Qari is hostile to our national interests.
Premise 2:
The state of Qari harbors many rare and desired natural resources.
Statement:
Invaders of a country often gain access to the country’s natural resources.
Conclusion:
Therefore, we should invade and occupy the State of Qari.
It seems pretty clear that this statement does, in fact, support the conclusion. Are we not assuming that invaders of a country often gain access to the country’s natural resources? Of course we are. That’s the only reason why Premise 2 pushes us towards the conclusion. If we thought that invaders didn’t get access to an invaded country’s rare and desired natural resources, then why would the resources’ existence motivate us to invade at all? That’s a rhetorical question. It wouldn’t.
Any given argument can have any number of assumptions. Some assumptions are logically sufficient, some are logically necessary, most are neither. We’ll focus on the distinctions between the different kinds of assumptions later (way later). For now, simply remember that an assumption is a premise that was left out of the argument.
LET’S REVIEW
Assumptions are premises that have been left out of the argument.
Featured image: ChessKnight-attribution-Loco
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Good v. Bad Arguments
WHEN WE SAY THAT AN ARGUMENT IS GOOD, WHAT DOES THAT REALLY MEAN?
Well, recall that an argument is just premise(s) plus conclusion. Premises support the conclusion and the conclusion is supported by the premises. “Good” simply describes how well the premises support the conclusion. In other words, “good” describes the strength of the support relationship between the premises and the conclusion. Just how “good” can the relationship be? Until it becomes perfect, of course. When that happens, it is said that the argument is valid. We’ll cover that concept later. For now, I want to turn your attention to the chart below:
That’s about as succinctly as I can explain the distinction between good and bad arguments. Bear in mind that most arguments in real life and on the LSAT do not have a valid relationship. Most arguments simply have a relationship where the premises, to varying degrees of strength, support the conclusion. Good ones make very few and very reasonable assumptions. Hence, their premises strongly support their conclusion. Bad ones make very many and highly uncertain assumptions. Hence, their premises weakly support their conclusion, if at all. The perfect ones make no assumptions and are said to be valid.
LET’S REVIEW
An argument is good to the extent to which its premises support its conclusion. The more assumptions an argument makes, the weaker the support the premises give to the conclusion and thus, the weaker the argument.
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Assumptions are Subtle
THIS STORY, I HOPE, WILL ILLUSTRATE SOMETHING VERY DIFFICULT ABOUT THE LSAT: ASSUMPTIONS ARE SUBTLE.
Why is that a difficulty? Because subtle things are, by definition, hard to notice. Yet, you are supposed to be very sensitive to assumptions, because they determine whether arguments are good or bad.
I worked at a law firm once. One of our clients was getting married to a movie star. The partner responsible for most of his private equity deals – something about money becoming more money – had to draft his prenuptial agreement. Of the numerous terms the parties were negotiating, I was working on the section that would determine how much their yet to be born children were worth. Our client instructed us to offer $100,000 per child as a lump sum alimony in the event of a divorce.
Anyway, I went to my office and started typing away. Under the divorce section, I dashed off:
“for each child born during the marriage, Party A agrees to transfer $100,000 to Party B…”
I checked for typos and emailed it to the partner. Later that afternoon, the draft was sent back with the following edits:
“for each child born of the two partiesduring the marriage, Party A agrees to transfer $100,000 to Party B…”
There was also a post-it note attached. In all caps and red ink it declared:
MALPRACTICE
Yikes.
The subtle assumption that I made was that “child born during the marriage” meant child born of the husband and wife during the marriage. I assumed fidelity in matrimony but of course people have affairs. Some of those affairs turn into pregnancies and some of those turn into bastards. The way I wrote the pre-nup, my client would have had to cough up alimony in the event that his wife cheats on him, gets pregnant, and gives birth to someone else’s child. The corollary would also have been true: if he had an affair and his mistress gave birth to a child, he also would have owed his wife alimony.
LET’S REVIEW
Don’t make assumptions.
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Logical Reasoning General Approach Revisited
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How to Weaken Arguments
TO WEAKEN ANY ARGUMENT, YOU HAVE TO UNDERSTAND ONE THING.
This thing is not tangible nor obvious. It’s instead abstract and subtle – which means it’s hard to understand.
Here it is: You have to take away the support. What support? The support that the premises give to the conclusion. Please read that again. I know it sounds very obvious, but please believe me when I tell you that it is not. And I promise you, the LSAT will get you on this a lot.
The reason is because you aren't used to doing this when you argue. When you argue, your instinct is to attack your opponent or simply contradict his premises.
For example, your friend claims that (conclusion) Avatar is the most touching movie ever because (premise) it's got that sad scene where the ship just sank and Kate Winslet is barely floating on that little piece of wood and Leo lets her stay on while he freezes to death.
What was your reaction just now? Was it something along the lines of "Wtf? Did the dumbass just confuse Avatar with Titanic?"
How would you respond? Maybe you'd say "Uh, hey man, there was no sad scene with Kate Winsl.. ah, nevermind. Please just go away."
Your first reaction was simply an attack on your friend. Your second response was simply a contradiction of his premise and then you asked him to leave.
Try to pay attention to arguments you witness from now on and you will find that so many of them are low level arguments like this one.
The LSAT isn't interested in arguments like this one.
The LSAT thinks that it's much more interesting to concede to your opponent his premises and then try to argue that despite your concession, his conclusion still doesn’t follow. In the example above, you concede to him that his premise was true, in other words, "for the sake of proper argument" let's say that scene was in Avatar, despite that being a totally unreasonable concession, your conclusion still doesn't follow.
And that’s exactly what Weakening questions test you on. It most certainly does not want you to contradict or attack a premise nor does it ask you to simply contradict or deny the conclusion. Instead, you are asked to deprive the support that the premises give to the conclusion, as if with magic.
Let me illustrate. Did you watch Dragon Ball growing up? Remember Goku’s Kamehameha? If not, I'm sorry. For your childhood because you missed out on some good shit.
Now pretend that little Goku is the premise and that car is the conclusion. The Kamehameha beam (i.e., the blue beam) is the “support.” The thicker the beam, the stronger the support and therefore, the stronger the argument. Think about it like that.
Accordingly, when you are asked to weaken an argument, you are asked to thin out the beam. But you can’t touch Goku, nor can you touch the car. Often, you have to fight your urge to attack (or contradict) the premise or attack (or contradict) the conclusion. You have to find something that thins out the Kamehameha beam. You have to find an answer choice that strips the existing premises of its supportive power. Don’t confuse that with attacking (or contradicting) the premises. You are not attacking (or contradicting) the premises. With the correct answer choice, you are demonstrating that despite the premises being true, it is now way less supportive of the conclusion being true.
SOME SAMPLE QUESTION STEMS
- Which one of the following, if true, is the logically strongest counter that Albert can make to Erin’s argument?
- Which one of the following statements, if true, most weakens the argument?
- Which one of the following, if true, most weakens the argument?
- Which one of the following, if true, most seriously undermines the conclusion drawn in the argument above?
- Which one of the following, if true, would most weaken the argument in the newspaper article?
LET’S REVIEW
Weakening questions ask you to weaken the argument. That means to weaken the relationship between the premises and conclusion. That relationship is the support relationship. That means you are to make the premises less supportive of the conclusion.
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Voice Mail - Weaken Question
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The Flowers Drew Received - Weaken Question
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Serious Medical Condition - Weaken Question
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Mathematical Principles - Weaken Question
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Prehistoric Paintings - Weaken Question
Featured image: Creative Commons License Jack Versloot
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Olympic Games - Weaken Question
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Animal Navigation - Weaken Question
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Society as Body Metaphor - Weaken Question
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Off Shore Oil Drilling - Weaken Question
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The Embezzler - Weaken Question
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Swimmer's Ear - Weaken Question
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Thread and Rope - Weaken Question
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Flammable Creosote - Weaken Question
This is an excellent explanation of the question pulled from a student's comments:
Maybe you can think of it this way.
Premise: wood-burning fires release cooler smoke up chimneys than open fires
Premise: this cooler smoke from wood-burning fires is more likely to create creosote and consequently ignite fires inside chimneys
Conclusion: wood-burning fires are more dangerous than open fires
The assumption here is that because wood-burning fires create more creosote which is conducive to igniting fires inside chimneys, that means wood-burning fires are more dangerous overall than open fires.
Another way to look at it is this. Despite the P being true that more creosote–>fires inside chimneys, there may be other factors that lessen the influence of that P in its support of the C. Such as (C), which suggests that open fires may not be less dangerous than wood-burning fires after all.
I think JY mentions the “not attacking the P or C directly” as a learning tool because often the ACs seem like they are weakening the P or C but in fact they are not. Much like (A).
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Blood Stain - Weaken Question
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