About this video
This video works through an LSAT-style weaken question. The argument says most people need vitamin pills because they do not eat five servings of fruits and vegetables a day. The presenter tests each answer choice and shows that only the one about commonly consumed fortified foods undermines the conclusion, because it suggests people get vitamins from other sources.
You'll be able to
- identify the conclusion and premise of a short argument and state what a weakener must do.
- judge whether an answer choice weakens an argument by checking it against the conclusion.
- rule out choices that are beside the point, reinforce the argument, or only justify a related claim.
Key words
- Weaken question
- A question asking which statement, if true, most undermines the conclusion of an argument.
- Conclusion
- The claim an argument is trying to prove, here that most people need to take vitamin pills.
- Premise
- A statement offered as evidence for the conclusion, here that most people do not eat five servings a day.
- Fortified food
- A food to which manufacturers add vitamins, which can supply nutrients people would otherwise lack.
- Beside the point
- An answer choice that does not affect whether the conclusion holds, and so cannot weaken it.
Transcript
- [Narrator] Nutritionists believe that a person's daily requirement for vitamins can readily be met by eating five servings of fruits and vegetables daily. However, most people eat far less than this. Thus, most people need to take vitamin pills. Which one of the following statements, if true, most seriously weakens, weakens.
We wanna weaken the argument. Alright, let's look at these choices. So choice A. So remember, what's the argument we're trying to make? We're trying to make the argument, or we're trying to weaken the argument that most people need to take vitamin pills. We wanna weaken that argument.
Which of these statements most weaken that? Choice A. Even five servings of fruits and vegetables a day is insufficient unless the intake is varied to ensure that different vitamins are consumed. So this doesn't seem to weaken it. If anything, it might slightly strengthen the argument because the argument's saying okay, if you eat five servings of fruits, then you might be okay, but most people don't do that, so you take pills.
But here they're saying even if you do the five servings, that still might be insufficient if your fruit isn't varied, so you still might need to take vitamin pills. So this seems to further reinforce the benefit of vitamin pills, so it's definitely not weakening.
So I will rule that out. B, certain commonly available fruits and vegetables contain considerably more nutrients than others. So, this seems a little bit beside the point. You know, maybe if you gave a little bit more depth here you could argue if you ate three servings of the right type of fruit, that that might be equivalent to five servings of other types of fruits, but then you would also have to make the case that most people are eating that, and only if you made all of those statements, or something like that, could it start to undermine, but this seems a little bit beside the point.
It seems to have no effect on the argument. So let me rule that out. Nutritionists sometimes disagree on how much of a fruit or vegetable constitutes a complete serving. Well once again, this seems a little bit beside the point. It doesn't really add or take away from it.
It's saying there's some debate on what a serving is, but it doesn't seem to undermine the notion that most people don't get their servings and therefore need to take vitamin pills. So let me rule that one out. Many commonly consumed foods that are neither fruits nor vegetables are fortified by manufacturers with the vitamins found in fruits and vegetables.
So this is interesting. This is saying that many commonly consumed foods are fortified with vitamins. So it's essentially saying hey, even though people might not eat as much fruits and vegetables as they need, they're still gonna get their vitamins because of the fortification of these commonly consumed foods.
So that, to me, seems to undermine that most people need to take vitamin pills, cause it's saying many people, or maybe even most people, are going to get their vitamins through this fortification of commonly consumed foods. So that does seem to weaken the argument.
Now let's just look at the last choice to see how we feel about it. Fruits and vegetables are also important sources of fiber, in forms not found in pills. So this doesn't weaken the reason, this doesn't weaken the justification for taking vitamin pills. It kind of justifies not giving up fruits and vegetables all together, saying that hey you still need to have fiber, but it doesn't weaken the argument that most people need to take pills, or at least the way it was given in the beginning, so I would rule that choice out as well.
I feel very good about D.
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