The question stem here reads, the argument depends on assuming that.

So again, we have a necessary assumption question, like question 9 for this set.

And we're going to do the same thing. We're going to find the premises, the conclusion,

and try to figure out what is missing. What is the gap between the premises and conclusion?

And the right answer choice has to absolutely be true.

So we're not really trying to strengthen the argument very much.

We're just, because there might be strengthening, there might be weakening answers,

there might be confusing wrong answer choices.

But what we're going to do is we're going to stick to our protocol for finding a necessary assumption,

which is that it must be true. In other words, if it's negated, then the argument falls apart.

have found to contain only half as much mercury as feathers recently taken from living birds of the same species.

So we're talking about seabirds and we're talking about 1800s versus now.

And what we know is that we find, I don't know, say like 5 units of mercury,

and now we find 10 units of mercury. This is from stuffed seabirds.

So since mercury that accumulates seabirds feathers, so yeah, where does it come from?

As the feathers grow, it's derived from fish eaten by the birds.

Ah, okay, so mercury just kind of accumulates as the birds age.

And not if they just like eat seeds, but if they eat the fish.

So it comes from the fish, we know that.

So already in this statement, we know two things about mercury.

It accumulates with age as the feather grows and accumulates with the amount of birds,

or rather fish, that you eat.

So these results indicate, so here comes the conclusion, that mercury levels in saltwater fish

are higher now than they were 100 years ago.

Well, I don't know. I mean, see this is a classic premise conclusion.

This is a classic phenomenon hypothesis type of setup.

So we call it premise conclusion. You can also think of it as phenomenon hypothesis.

We observe these things that, you know, a bird suffered from 1800s, 5 units of mercury.

Now, 10 units of mercury. We know that, you know, this is where mercury comes from.

And then from this set of phenomena, we're trying to provide an explanation, a hypothesis.

And our explanation is that, oh, it's because, you know, the fish now just have more mercury

in their systems than they did 100 years ago.

Now, that is a plausible hypothesis.

It's a hypothesis that's consistent with all the information we have with the phenomenon.

But it's not the only hypothesis.

So it depends on assuming what? It depends on assuming a lot of things.

You know, can you think of an alternative competing hypothesis?

For example, what if they just didn't eat as much fish back then?

You know, the fish contains equal levels of mercury, but it's just they ate a lot of other stuff.

Right? They just didn't eat as much fish.

Okay, that's fine. What if they didn't live as long?

You know, we know that they grow, right?

What if these are, you know, they live like two years, they're young seabirds,

and they just die because conditions are bad.

Now they live to be a ripe age of 20 years.

So they have like 18 more years to accumulate mercury.

That doesn't mean that the fish, mercury in saltwater fish are higher.

It just means they live longer.

So all these things, it's just two things you have to accommodate.

There could be plenty more things you have to accommodate, competing hypothesis you want to block.

So in that sense, you know, it's very similar to strengthening and also weakening questions

that use this type of logic, causation, phenomenon, hypothesis, you know, phenomenon, explanation type of setup.

So argument depends on assuming.

It was lower on average in the 1800s.

But that's bad, actually.

You see, we need to say it's just as high.

Because if they ate less fish, right, they ate, you know, proportionally less fish in the 1800s,

then that is an explanation of why maybe this is lower.

But we're not looking for that.

We're not weakening.

So if this were a weakening question, the argument is vulnerable,

or which one following if true most weakens argument.

If it weakens, it's a weakening question, then this would actually be right.

I think this would be right.

I'm pretty sure it would be right.

We won't ever know because it wasn't a weakening question.

But, right, you see, it certainly is not necessary.

We don't want to assume this.

We want to assume the opposite of this.

That's totally not what we're being asked to do.

I don't really care what it depends on.

You see, like, this question is baiting you to think about, oh, you know, it must be that we're more polluted now

than we were in 1800s, so something about more mercury.

I don't really care where the mercury in saltwater fish come from.

It could have come from pollution.

It could come from, I don't know, name your source.

It just doesn't matter.

All we care about is the birds have feathers, which has mercury in it, which comes from the fish that they eat.

Where that comes from, don't care.

That's great.

You know, so mercury is sometimes essential.

And must that be true?

What if it's not essential?

What if it's just purely poisonous?

That doesn't do anything to our argument.

We don't need mercury to be essential for growth of the seabird's feathers.

If it's not, this argument is, you know, this hypothesis is still as plausible of an explanation for the phenomenon as it ever was.

That's actually bad.

See, this is very similar to A.

Right, where is this?

Very, very similar to A.

If this were the, if this were the case, what are the case?

They're just baby seabirds.

That kind of explains why maybe the mercury levels are lower.

Versus living seabirds, well, they have to also accommodate that.

Whereas the seabirds that we tested now are fully grown seabirds.

If you amend that to D, then D does sort of like A, weaken the argument.

But again, we're not asked to weaken the argument.

We're being asked to identify a necessary assumption.

Yeah, that has to be true.

What if the explanation was that, oh, when you made the seabirds into stuffed seabirds, that preservation technique, that's what halved the level of mercury.

If that's the case, then you certainly can't say that this is indicative of the saltwater fish having higher mercury levels now.

Right, it's because through the process of preservation, the mercury levels were halved.

So you have to accommodate, you have to sort of block this from being possible.