Weakening concepts and truth vs validity

[Kmikaeli]

Hey guys, I am having problems grasping the concepts pertaining to weakening questions. The section states that there will be errors of assumption present within these arguments which makes them flawed. However, I do not understand how the common weakening scenarios deal with assumptions and the conclusion? HOw do they attack assumptions to weaken conclusions? Furthermore, do the three incorrect answers for weakening questions deal with incorrect assumptions or conclusions? It is difficult for me to grasp the concept while wondering if the scenarios weaken the assumptions or the conclusions and what not. (Logical Reasoning Bible 2014 pg 221-222) Also, in the beginning of this book you guys state in the "truth and validity" portions how truth deals with "how a conclusion is true relative to the premises". However, doesn't the statement "If the premises are accepted, how well do they prove the conclusion?" target both truth and validity?

[Dave Killoran]

Hi Kmikaeli,

Let's see if we can help out here. One of the issues is that you are mixing a lot of ideas together, so let's separate some of that out first

Errors of assumption occur constantly on the LSAT, and as will be explored in more detail in a later chapter, an assumption doesn't always mean that you assumed something was the case; in many instances, assumptions revolve around assuming something is not the case. So, for example, Improper Comparison answers assume that the two items are essentially similar and that no relevant differences occur. The conclusion then makes a judgment based on that mistaken assumption, and the correct weakening answer often points out this problem. Incomplete Information answers assume that the author had all the accurate or relevant data and that no important data was missing, and then make a similarly flawed conclusion. However, the three types there are just broad ideas to get you thinking—they aren't the only three types of Weakening answers in existence. That said, I do have a suggestion given the questions you posted, and that is that it might actually be worth your while to jump ahead to Chapters 11 (Assumption) and 15 (Flaw in the Reasoning) and scan through those (there will be elements from interim chapters that you won't have seen yet, but just bypass that stuff for now in the interests of getting a bigger picture view of these ideas).

With truth and validity, let's go back and look at the comments I made there, because I think that may help here. I'll add some italics as well to help clarify. I said, "When we evaluate LSAT arguments, we are primarily concerned with validity. That is, what is the logical relationship of the pieces of the argument and how well do the premises, if accepted, prove the conclusion? We are less concerned with the absolute, real world truthfulness of either the premises or the conclusion...In most cases, the LSAT makers will let you work under a framework where the premises are simply accepted as factually accurate, and then you must focus solely on the method used to reach the conclusion. In a sense this could be called relative truthfulness—you are only concerned about whether the conclusion is true relative to the premises, not whether the conclusion is true in an absolute, real world sense."

You might be able to tell I'm walking a fine line there—"truth" is an issue of some significance in the logical/philosophical realm, but at the same time I didn't want to get too deeply into it since it's not as important in the LSAT world. With that in mind, the statement that "If the premises are accepted, how well do they prove the conclusion?" is built around how that works from a logically valid standpoint. Depending on how you define truth (using a real world or philosophical definition changes things), you can say that truth plays a role, but I would say don't get caught up in worrying about the definition. Instead, ask yourself if the conclusion makes sense or if it is proven by the given premises. That will typically do the trick, especially because the LSAT itself won't get into the "truth" issue.

Please let me know if that helps. Thanks!

[Kmikaeli]

I now understand that truth is not really something to get caught up in, but instead ask myself that if the premise proves/supports the conclusion in order to determine if the conclusion is valid. If the premises do not support the conclusion or the conclusion is is not derived logically from the given premises, then we know that the argument is weak and flawed. This makes sense to me.

However, for the weakened questions and scenarios, let me see if I got a right mindset.

So the three scenarios given are common weakening scenarios that exist within these types of questions. The improper comparison essentially is the author believing that he is making sense of premises that are essentially different, and my job is to make that assumption that there is an improper comparison in order to weaken the conclusion?

[Nikki Siclunov]

Hi Kmikaeli,

Thanks for the question. When we speak of weakening arguments in logical reasoning, we always mean one thing, and one thing only: weakening their conclusions. An argument is valid if and only if its conclusion is logically entailed by its premises: the conclusion must be a logical consequence of the premises upon which it is based. To weaken any argument, you need to show that the conclusion does not necessarily follow from the premises. The truth of the premises is assumed, and should not be questioned (unless the stem specifically asks you to do so, which they have done only once in the last 20+ years).

How do you show that the conclusion is not logically supported by the premises? That's where the author's assumptions come into play - the unstated premises upon which his/her argument is based. Unless an argument is 100% valid, i.e. unless its premises fully and completely prove the conclusion - that argument contains implicit assumptions that we can exploit. To weaken an argument, a good strategy would be to question some of the less warranted assumptions upon which the conclusion is based. Let me give you an example:

Sociologists recently found that the divorce rate in Maine strongly correlates with Maine's per capita consumption of margarine. If you want to save your marriage, stop consuming margarine at once!

In this argument, the author clearly assumes that the observed correlation indicates a causal relationship between margarine consumption and divorce. To weaken the conclusion, we need to show that this relationship is not logically entailed by the premises. First, the correlation may be pure coincidence. Second, it is possible (though arguably less likely) that people who divorce hope to get in shape in order to attract new mates, and so they forfeit butter for the sake of margarine. It's a stretch, but - if true - it shows that the causal relationship may be reversed. Third, we can argue that a third factor - higher levels of stress, perhaps - causes people to consume more fat (including margarine) but also increases the divorce rate in Maine.

As you can see, we just weakened the conclusion by undermining the unwarranted assumption that a correlation is sufficient to prove a causal conclusion.

Identifying unwarranted assumptions is foundational to critical thinking. For any argument that is not logically valid, you need to wonder what additional premises are necessary for the conclusion to be logically valid. By showing that these assumptions are not necessarily true, you can effectively weaken the conclusion(s) based upon them.

Let me know if this makes sense!

Thanks.

[Kmikaeli]

That makes perfect sense, but one last thing; How do the weakening scenarios (incomplete info. incompatible comparison, and overly broad conclusion) play a role in making assumptions to weaken the conclusion?

[Dave Killoran]

Hi Kmikaeli,

I think Nikki and I were both answering your original question at the same time, but his posted after your followup question However, what he said is extremely helpful in understanding weakening in general, so definitely check that out as well.

You asked:

However, for the weakened questions and scenarios, let me see if I got a right mindset.

So the three scenarios given are common weakening scenarios that exist within these types of questions. The improper comparison essentially is the author believing that he is making sense of premises that are essentially different, and my job is to make that assumption that there is an improper comparison in order to weaken the conclusion?

Yes, you are correct, these are some of the problems you see within argument (and many more are presented in the Flaw chapter I referred you to above).

With the Improper Comparison portion, I would change that to read (changes in italics): "The improper comparison essentially is the author equating ideas that are essentially different, and my job is to recognize that assumption that improper comparison in order to understand why conclusion is weak." So, along the lines of what you were saying, but with some minor changes to make it a bit more accurate.

Please let me know if that helps. Thanks!

[Kmikaeli]

You guys are awesome, so far I got everything you two have explained.

Just one last minor bug I keep coming across is the word reasoning. When you guys present conditional REASONING, does that basically mean making sense of conditional statements in relation to the argumentative question and the argument itself? I know this is random, but when reasoning is introduced in topics such as Causal Reasoning, I get confused what reasoning means since its so abstract a term.

[Dave Killoran]

Great, glad we are helping!

Reasoning is just the process of argumentation—drawing conclusions from premises. So, you can have specific types of reasoning—such as causal or conditional—and it just means reasoning that uses those specific forms.

Thanks!

[Kmikaeli]

Okay, I'm running through problems again.

Incomplete information: This is where the author does not present enough information through premises, and I have to make an assumption counter to the one the author has made through his evidence?

Improper Comparison: Where I assume that the author has correlated different premises that are not connected?

Broad Conclusion: I assume that the author has made a broad conclusion?

[Dave Killoran]

Hi Kmikaeli!

Let's take a step back from this for a second, because I want to realign how you are thinking about these questions just a bit In these questions, your goal is to recognize when the author has made an assumption. Based on what you see, you will then be better able to recognize what error has occurred. So, you aren't making an assumption, you are looking to see if the author made one. Then, when you do see where the author went wrong, you are looking for an answer that exploits or takes advantage of that weakness.

In this sense, you are like an air traffic controller—you are looking for things when they appear on your radar. You aren't the one making assumptions.

Please let me know if that makes sense. Thanks!