Logical Reasoning

PT146 · S3 · Q25 At Morris University this semester

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At Morris University this semester, most of the sociology majors are taking Introduction to Social Psychology, but most of the psychology majors are not.

Conclusion

There must be more sociology majors than psychology majors enrolled in Intro to Social Psychology.

Evidence

Most sociology majors are taking it. Most PSY majors are not taking it.

Evaluate

Because this argument has conditional/quantified terms, we could potentially get it right without understanding the flaw, as long as we convert it into a symbolic recipe.

Most A's are in place X. Most B's are not in place X. Thus, there are more A's than B's in place X.

The flaw revolves around the fact that we're making two Most claims, but they're about different groups. You can't really compare such claims without knowing about the relative size of those different groups.

For example, let's say at Morris University that there 100 sociology majors and 1000 psychology majors.

Most sociology majors are in this class, so at least 51 sociology majors are there. Most psychology majors are not in this class, so at most 499 psychology majors are there.

Have I convinced you that this class has more sociology majors than psychology majors? Of course not. There might be way more psychology majors present, if the group of all psychology majors is bigger than the group of all sociology majors.

Goal

Look for two Most premises, and a conclusion saying one number is bigger than another.

Look for something resembling this recipe: Most A's are in place X. Most B's are not in place X. Thus, more A's than B's in place X

Or look for an argument similarly vulnerable to the objection of,

25.

The flawed pattern of reasoning in the argument above is most similar to that in which one of the following?

  1. Most of the paintings on

    Bad Conclusion Match

    We do have two Most premises, but the conclusion isn't saying that one quantity is bigger than another, so there's no reason to dig deeper here.

    4% picked this

  2. In an opinion poll of

    Bad Premise / Conclusion Match

    There's only one premise, so that's an immediate deal breaker. The conclusion also isn't saying that one quantity is bigger than another (it's saying, "most people prefer one thing over another").

    4% picked this

  3. In the San Felipe city

    Bad Premise Match

    There's only one premise, so that's an immediate deal breaker. The conclusion, to its credit, is lovingly saying that one quantity is bigger than another.

    11% picked this

  4. Correct

    Most of the vegetables available

    Why this is right

    From a bird's eye view, it's got two Most premises and a conclusion that compares quantities. Here's how it would match with the original argument. Most SOC are taking Intro to SP Most available veggies at VCF are organic. Most PSY are not taking Intro to SP Most available veggies at JS are not organic. So, more SOC than PSY are taking Intro to SP More VFC veggies than JS veggies are organic Both arguments are vulnerable to the objection, "What if one of those groups is much bigger? If Jumbo Supermarket sells 1000 vegetables, but Valley Co-op sells 100, Valley Co-op sells a minimum of 51 organic. Jumbo sells a maximum of 499 organic. So there might be more organic vegetables available at Jumbo.

    Skill tested: Parallel Flaw · how this choice captures the argument's function is the move to repeat next time.

    64% picked this

  5. The Acme Realty website has

    Weaker Match

    This one is very close. There are two Most premises (if we hear the first two claims as "most houses for sale have a website photo" and "most condos for sale do not have a website photo"), and the conclusion is indeed a quantitative comparison. And this is also vulnerable to the "what if one group is much bigger" objection. If there are 1000 condos for sale, and only 100 houses for sale, then at least 51 of the houses would have photos on the site and at most 499 condos would have photos on the site. A matching conclusion, though, would have said, "So there must be more photos of houses on the website than there are photos of condominiums." This conclusion went one level farther by talking about the total number of houses / condos for sale. This argument is also vulnerable to a different kind of objection, one that isn't mathematical in nature, but Causal Hey, author, maybe there aren't fewer condo photos on the website because there are fewer condos for sale but just because website pictures of condos aren't as sexy as website pictures of houses.

    17% picked this

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