Q20 - All orchid species that are

[csunnerberg13]

I just wanted to make sure I understood this flaw correctly, since the answer choice wasn't worded in a way I was used to.

I thought the flaw here was an illegal reversal. Is (D) another way to say that it confuses a necessary and sufficient assumption?

thanks

[ohthatpatrick]

You're exactly right.

The core is
PREM:
Pollinated solely by insects --> feature that attracts insects
+
X has a feature that attracts insects
CONC:
so, X is pollinated solely by insects

When we recognize that conditional logic was botched, that's Nec/Suff Flaw, but we still have to stay flexible for other ways the answer choice could be worded.

For instance, the correct answer could have been:
"fails to consider that orchid species that are not exclusively pollinated by insects may also have features that attract insects".

The wording of (D) actually IS Nec/Suff, but I agree it's pretty unusual wording.

If I say a characteristic that is known to be true of one class of things, we would write that as:
Class of things ---> Characteristic
or
Former US President --> Male

Is the characteristic of "Male"-ness unique to that class of former US Presidents? Of course not. I have the characteristic of male-ness, and the highest office to which I rose was President of the School Patrols (i.e. crossing guards).

If a characteristic WERE unique to a class of things, it would be fair to say
Characteristic --> Class of Things.

So this answer choice expresses the same reversal of logic we're expecting with a Nec/Suff flaw.

[jones.mchandler]

Could you explain the wording of D a little more in depth? I'm unclear as to how the argument is treating a characteristic known to be true of one class of things as if it were unique to that class. It seems like that would require some sort of exclusion like "no other species of flower has this trait" or something along those lines. I'm just not sure how the argument is doing what D says. The other ACs were wrong, but this is just the oddest wording of this type of flaw I think I've ever seen.

edit: So I was looking at this question again today and trying to make sense of TCR, and it started to remind me of a very basic question that I came across once. It was number 1 on some PT, and it was a flaw question...it was something along the lines of "this person thinks this unidentified substance is iron. To test this, the person put the substance by a magnet, bc they know that magnets attracts iron. the substance was attracted to the magnet, and therefore the substance is iron." Obviously the flaw is that other substances could be attracted to magnets. Is saying "treats a characteristic known to be true of one class of things as if that characteristic were unique to that class" the same flaw as the iron/magnet question?

[ohthatpatrick]

Yes, exactly! Great job building connections between problems.

Consider this argument:
This animal has a tail.
Thus, it follows that this animal is a dog.

Not very convincing. What am I assuming?

I'm assuming that "only dogs have tails", or "tails are UNIQUE to dogs".

Does it help if I tell you that "all dogs have tails"?

No! Because so do all cats, cows, goats, horses, etc.

I still don't know just because this animal has a tail that it MUST be a dog.

Similarly, the author is saying:
This orchid has features that attract insects.
Thus, it follows that this orchid is pollinated solely by insects.

To make the move from Fact 1 about "this orchid" to the Conclusion about "this orchid", you have to assume that "features that attract insects are only found on orchids that are pollinated solely by insects".

If we symbolized that assumption as a conditional statement, we'd get:
features that attract insects --> pollinated solely by insects

Naturally, that's a reversal of the first sentence.

For extra practice think about how you would conditionally diagram "a characteristic known to be true of one class of things".

Would you say:
characteristic ----certain---> that class of things
or
that class of things ---certain---> characteristic

You say the 2nd, because the characteristic is known to be true

Meanwhile, "a characteristic that is unique to a class" goes the other way
characteristic ---certain--->that class of things

Writing poetry is unique to human animals.

Does that mean
human --> write poetry
or
write poetry --> human?

Again, the 2nd one.

Hope this helps.

[MeenaV936]

I understood the flaw (illegal reversal) and knew the answer would confuse sufficient and necessary conditions, but I chose B. Why is B wrong? Isn't it also saying that the sufficient and necessary conditions have been confused, as indicated by the language that the characteristic "distinguishes" (sufficient condition) vs. the characteristic is the "only thing that distinguishes" (unique/necessary condition)? Please advise -- thank you!

[ohthatpatrick]

Here's an argument that would be vulnerable to the objection spelled out in (B).

A Patrick Orchid is different from other orchids in that it has the ability to do Logic Games. Thus, it must be similar to other orchids in terms of length and color of its petals.

For (B)'s argument, you start by learning that quality X is unique to thing A, and then you hear the author assuming that quality X is the only unique quality to thing A.

Did the argument in Q20 start off by defining "a characteristic that distinguishes one class of things from another"?

It did not. I can tell you "All lions have beating hearts". That doesn't tell you that 'beating hearts' is a characteristic that distinguishes lions from other classes of things.

Similarly, maybe all orchid species that are 100% insect-pollinated have features attractive to insects. And maybe all daisy species that are 100% insect-pollinated ALSO have features attractive to insects.

What we learn about orchid species in sentence 1 doesn't distinguish it from other classes of things, so we can stop reading (B) at that point.

Contrast that wording with (D)'s:
Does the first sentence discuss "a characteristic known to be true of one class of things"?

Yes. I know that all orchid species that are 100% insect-pollinated (a class of things) have features attractive to insects (a characteristic).

Does that make sense?