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Valid vs. Invalid Arguments

FutureSportsLawyerFutureSportsLawyer Alum Member
in Logical Reasoning 109 karma

So I think i'm confused at how these are different. I completely understand the definitions of valid and invalid arguments. I'm just confused at how you would be able to distinguish these two things on the LSAT. Does the question stem typically tell you it wants "invalid" or "valid" or will you just have to make a decision based off the stimulus?

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  • akistotleakistotle Member ⭐ 🍌🍌
    9382 karma

    @FutureSportsLawyer said:
    I'm just confused at how you would be able to distinguish these two things on the LSAT.

    Hmmm. If you can't identify invalid arguments on the LSAT, maybe you should go back to the CC.

    Does the question stem typically tell you it wants "invalid" or "valid" or will you just have to make a decision based off the stimulus?

    Have you drilled flaw questions? If you are ok with "burning" PT23, you should take a look at this question (PT23.3.17) and figure out what the stimulus is doing:
    https://7sage.com/lsat_explanations/lsat-23-section-3-question-17/

  • FutureSportsLawyerFutureSportsLawyer Alum Member
    109 karma

    I haven't. I just finished reviewing the valid and invalid argument types and I was more confused on how it would be presented as a question if that makes sense. But that gave me a better understanding on how it would be shown.

  • AlexAlex Alum Member ⭐
    23929 karma

    @FutureSportsLawyer said:
    I haven't. I just finished reviewing the valid and invalid argument types and I was more confused on how it would be presented as a question if that makes sense. But that gave me a better understanding on how it would be shown.

    Yeah, definitely re-watch the lessons on them.

    Can you elaborate on exactly what you are having trouble understanding?

  • akistotleakistotle Member ⭐ 🍌🍌
    9382 karma

    @FutureSportsLawyer said:
    I haven't. I just finished reviewing the valid and invalid argument types and I was more confused on how it would be presented as a question if that makes sense. But that gave me a better understanding on how it would be shown.

    So are you saying that you don't know how the concept of validity is relevant to LSAT questions? If you start doing more questions, you will see. :smile:

  • FutureSportsLawyerFutureSportsLawyer Alum Member
    109 karma

    I'm just confused as to how I'm supposed to see these chains within the questions on the LSAT. Especially in a minute. That just doesn't make sense to me. It makes sense as I do the lessons, but when I look at actual questions, I don't see those in my head. I probably sound insane but I don't really know how to word my confusion!

  • akistotleakistotle Member ⭐ 🍌🍌
    9382 karma

    @FutureSportsLawyer said:
    I'm just confused as to how I'm supposed to see these chains within the questions on the LSAT. Especially in a minute. That just doesn't make sense to me. It makes sense as I do the lessons, but when I look at actual questions, I don't see those in my head. I probably sound insane but I don't really know how to word my confusion!

    Are there any specific questions that confused you?

  • BinghamtonDaveBinghamtonDave Alum Member ⭐ 🍌🍌
    8711 karma

    Ok, so the piece that I think might be missing here is colloquial definition of what a valid argument actually means and how we can apply that understanding to the LSAT. I used to view the valid/invalid arguments with a similar degree of confusion.

    A valid argument is a set of premises structured in such a way that it yields a supportable/valid conclusion. That structure of the argument follows certain rules that in the abstract repeat on questions. So if I were to tell you: if something is a cat then it is a mammal, that follows a basic structure that says: If A then B. A valid argument could look something like: If something is a cat then it is a mammal, Lil Bub is a cat, therefore Lil Bub is a mammal. That follows a pattern that we benefit from knowing: we are given If A then B, we are then provided with a specific A (Lil Bub) and we are allowed to draw the conclusion B (is a mammal.) Being allowed to draw a conclusion is what makes the argument valid. I think of a valid argument as a solid foundation in which a conclusion rests. There are several different ways in which we can build this solid foundation for our conclusion to rest. We could say: if something is a cat then it is a mammal and all mammals are warm blooded. Lil Bub is a cat, therefore: Lil Bub is warm blooded. Here we have the
    A---->B----->C foundation in which we support our conclusion.

    Now, an invalid argument is a foundation that does not support the conclusion provided, or potentially, no conclusion at all. An invalid argument is a terrible foundation. Lets take the previous example: if something is a cat then it is a mammal. This orca whale is a mammal therefore...? We cannot work backwards after we have affirmed the necessary condition. That would lead to say that "this orca whale is a cat." Now, on the LSAT, this bad form won't be that recognizable by the actual entities presented (in this case we know that orca whales are not cats) but rather by the form:
    If something is an A then it is a B
    We have a B here
    that doesn't't mean we have an A.

    This is just a cursory view here. The key and the reason why learning these forms is important is to wield against a complicated stimulus is an effective way. Stimuli on this exam might be talking about particle physics or some complicated argument about morality or language. What is important is to be able to pin down the abstract form in an efficient way.

    I hope this helps, it took me a long time to get the hang of the argument forms and their utility.

    David

  • smartaone2smartaone2 Alum Member
    513 karma

    @BinghamtonDave said:
    Ok, so the piece that I think might be missing here is colloquial definition of what a valid argument actually means and how we can apply that understanding to the LSAT. I used to view the valid/invalid arguments with a similar degree of confusion.

    A valid argument is a set of premises structured in such a way that it yields a supportable/valid conclusion. That structure of the argument follows certain rules that in the abstract repeat on questions. So if I were to tell you: if something is a cat then it is a mammal, that follows a basic structure that says: If A then B. A valid argument could look something like: If something is a cat then it is a mammal, Lil Bub is a cat, therefore Lil Bub is a mammal. That follows a pattern that we benefit from knowing: we are given If A then B, we are then provided with a specific A (Lil Bub) and we are allowed to draw the conclusion B (is a mammal.) Being allowed to draw a conclusion is what makes the argument valid. I think of a valid argument as a solid foundation in which a conclusion rests. There are several different ways in which we can build this solid foundation for our conclusion to rest. We could say: if something is a cat then it is a mammal and all mammals are warm blooded. Lil Bub is a cat, therefore: Lil Bub is warm blooded. Here we have the
    A---->B----->C foundation in which we support our conclusion.

    Now, an invalid argument is a foundation that does not support the conclusion provided, or potentially, no conclusion at all. An invalid argument is a terrible foundation. Lets take the previous example: if something is a cat then it is a mammal. This orca whale is a mammal therefore...? We cannot work backwards after we have affirmed the necessary condition. That would lead to say that "this orca whale is a cat." Now, on the LSAT, this bad form won't be that recognizable by the actual entities presented (in this case we know that orca whales are not cats) but rather by the form:
    If something is an A then it is a B
    We have a B here
    that doesn't't mean we have an A.

    This is just a cursory view here. The key and the reason why learning these forms is important is to wield against a complicated stimulus is an effective way. Stimuli on this exam might be talking about particle physics or some complicated argument about morality or language. What is important is to be able to pin down the abstract form in an efficient way.

    I hope this helps, it took me a long time to get the hang of the argument forms and their utility.

    David

    Thank you! This is a great explanation and it helped me better understand what an "invalid" argument looks like.

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