Flaw Questions and Logical Flaws IV

Transcript

Hello and welcome to lesson four of law questions and logical flaws. In our previous three lessons, we covered 8 out of the 11 standard logical flaws, concept shift all the way to circular reasoning. And in this lesson, we will be covering the last three, appeal to authority, personal attack, and the part to whole or whole to part fallacy. Let's start off with appeal to authority.

Go ahead and pause the video, read this argument, and think about why the conclusion does not necessarily follow from the premise. So the conclusion here is the last sentence. Thus, we can be confident that we will not find life on other planets. And the reason given in support of that is that the vast majority of scientists believe that life does not exist outside of Earth.

But does the fact that the vast majority of scientists think that life doesn't exist outside of Earth mean that that's true, that life doesn't exist outside of Earth? Of course not, couldn't they just be wrong? Couldn't the scientists just be having a belief that is incorrect? And that is exactly why this argument is flawed.

Remember, just because an expert believes something does not prove that that belief is true. Experts can be wrong, and maybe there's other experts who disagree. So don't automatically trust something just because an expert says it. You should also note that reliance on an expert's belief is even more inappropriate when the subject of the claim is outside of the expert's realm of expertise.

So for example, in this argument above about extraterrestrial life, what if instead of asking scientists, we asked doctors or dentists what they thought about life outside of Earth? If we did that, then we would have even less reason to believe that their claim is true, or to use the fact that they believe something as evidence that the claim is true.

This kind of flaw is called the appeal to authority because the premises of the argument don't give you any independent reason to believe the conclusion. The only thing they do is, they rely on some expert, some authority figure. So how does the LSAT word this kind of flaw? Well, we can see that over here, the argument relies on the testimony of experts whose expertise has not been shown to be sufficiently broad to support their claim.

So let's take a look at the next flaw, the personal attack. Go ahead and pause the video, read the argument, and think about why the conclusion doesn't necessarily follow from the premises. So the conclusion of this argument is the last sentence. Thus, we know that the governor's claim is false. What was that claim?

Well, it was that he did not encourage anyone to engage in voting fraud in this year's governor election. So basically, the conclusion is saying he did encourage people to engage in voting fraud. But what's the reason given for why we know that he encouraged people to engage in voting fraud?

It's this line, the premise, because he previously admitted to lying about his educational credentials, and was convicted of tax fraud before he won his first election. But does the fact that he lied about his educational credentials, and that he committed tax fraud in the past, prove that he encouraged people to commit voting fraud in this year's election?

Of course not, the past is the past. It doesn't have any bearing on what he did or did not do in this year's election. So the problem with this argument is, it is simply making a personal attack on the background or the character of the source of a claim. The governor made a certain claim. And we're saying, because of his background, because of certain bad things he did in the past, his claim must be wrong.

But that of course is flawed reasoning, because if we really wanted to evaluate the truth of the governor's claim, we have to evaluate it on the merits. The background of the person who made the claim is not sufficient to prove that that claim is true or false. Just because someone lied in the past does not make what they're saying now a lie. If we really wanted to evaluate whether the governor encouraged voting fraud, then we have to look at evidence.

We can't just rely on the background or the character of the person who made that claim. Now, you might recognize that this kind of argument happens all the time in modern-day politics. But of course, that is outside the realm of logic. And on the LSAT, a personal attack is not an appropriate way to make an argument.

So when this flaw appears on the LSAT, how is it worded in the answer choices? Well, it looks like this, criticizing the source of a claim rather than examining the claim itself. The last flaw is the part whole fallacy, sometimes called the composition fallacy. Now, there are two forms of the part whole fallacy. One version is going from the part to the whole, and the other version is going from the whole to the part.

Go ahead and pause the video, read this argument, and think about why the conclusion doesn't have to follow from the premise. So here, the conclusion is that my friend will enjoy the dish that I'm making for him, pizza that has chocolate, sushi, and watermelon. What's the reason given for why my friend is going to enjoy pizza with chocolate, sushi, and watermelon toppings?

Well, it's because he enjoys chocolate, pizza, sushi, and watermelon by themselves, they're each among my friend's favorite foods. But does the fact that he enjoys each of those foods by themselves necessarily mean that he's gonna enjoy a pizza that has all those toppings? Not necessarily, because maybe he's not gonna enjoy the combination of sushi and chocolate.

Maybe that's just a flavor combo that he will disapprove of. So the reason this question is flawed is that, just because something is true about individual parts does not mean that it's going to be true about all those parts put together. In this case, just because chocolate, pizza, sushi, and watermelon are foods that he likes, doesn't mean that when you put it all together, he's gonna like that combination.

This argument is going from part to whole. The premise is about the part, and the conclusion is about the whole. Let's take a look at the other version of this flaw. Go ahead and pause the video, think about why this argument doesn't make sense. The conclusion here is that each of the members of the Randle University relay team must be a fast runner.

And how do we know that each of them must be fast? Well, because the team itself is extremely fast and consistently gets the best times at their races. But just because the relay team is fast, does that mean that each of the members of the relay team is also fast? Isn't it possible that maybe there's three really, really fast runners and one runner who is extremely slow?

So maybe the team itself is winning, but they could be winning largely because of the three really fast runners. And the one slow runner isn't really helping them all that much. So the reason that this argument is flawed is that, just because something is true about the whole does not mean it's true that each of the individual parts. So just because the team itself is fast does not mean that each of the members is also fast.

This argument is going from whole to part, the premise is about the whole, the conclusion is about the part. So how are these flaws commonly worded when they appear in the answer choices? Well, here's the part to whole version, improperly draws an inference about the whole from a premise about individuals. The argument is improperly drawing an inference about the whole, which is this pizza, chocolate, sushi, watermelon combo, from a premise about the individuals, the individuals being each of the foods by themselves.

And here's how the whole to part is worded on the LSAT, infers that a part has a quality merely from the fact that the whole to which it belongs has that quality. So infers that each of the members has a particular quality of being fast, just because the whole that they belong to, the team, is fast. So remember, this flaw has two versions, one that goes from part to whole and one that goes from whole to part.

And on the LSAT, it does matter which one the argument is doing when there is this composition or part whole fallacy. So now you've seen the 11 standard flaws on the LSAT. Make sure you study this list, and review the prior lessons if any of these flaws is a little bit shaky in your mind. It's important that you understand each of these flaws very well, because they're going to appear all over logical reasoning.

Although not every flaw question commits one of these flaws, many of them do. And in addition, these flaws appear on other kinds of question types too besides flaws. Basically, any argument-based question that involves a flawed argument, like strengthen or weaken or assumption questions or parallel flaw. Any of those problems could potentially raise one of these flaws.

So if you master these flaws, you'll be well on your way to mastering logical reasoning.