words that possibly introduce a necessary condition Forum

[naillsat]

I keep wondering whether words/phrases like "suggest", and "as long as" introduce a necessary condition. For example:

The good grades that Tom got suggest that he studied hard.

Bicycle stays stable only as long as it keeps moving forward.

"studied hard" for certain is a necessary condition, but how about the phrase "as long as"? does it also indicate a necessary condition for most of the time?

[timmydoeslsat]

I keep wondering whether words/phrases like "suggest", and "as long as" introduce a necessary condition. For example:

The good grades that Tom got suggest that he studied hard.

Bicycle stays stable only as long as it keeps moving forward.

"studied hard" for certain is a necessary condition, but how about the phrase "as long as"? does it also indicate a necessary condition for most of the time?

As long as = sufficient condition. However, in the context of your sentence with the placement of only before that phrase, we have that as a necessary condition. Same structure holds true of a word like when.

It snows when it is cloudy.
It only snows when it is cloudy.

Although when is used in both statements, the word of only changes the meaning of conditions. In the first, cloudy is sufficient to bring about snow. In the second statement, the idea of snowing means necessarily that we have cloudy.

So for your example of the bicycle staying stable only as long as it keeps moving forward:

Bike stable ---> Keeps moving forward

If you were to say instead that the bike stays stable as long as it keeps moving forward:

Keeps moving forward ---> Bike stable
The other example of suggests is not sufficient or necessary. It is an unreliable relationship that cannot be diagrammed without conditional indicators.

[dowu]

[naillsat]

another example with "as long as"

As long as you study hard, you can get a 180 on the LSAT.

My suspicion is "studying hard" never guarantees a 180. Is it still a sufficient condition? maybe that's why I used "can" in this above sentence.

[timmydoeslsat]

another example with "as long as"

As long as you study hard, you can get a 180 on the LSAT.

My suspicion is "studying hard" never guarantees a 180. Is it still a sufficient condition? maybe that's why I used "can" in this above sentence.

Exactly. As long as = sufficient condition.

Study hard ---> Can get 180

[wlees]

It snows when it is cloudy.
It only snows when it is cloudy.

Although when is used in both statements, the word of only changes the meaning of conditions. In the first, cloudy is sufficient to bring about snow. In the second statement, the idea of snowing means necessarily that we have cloudy.

As much as I believe I understand conditional reasoning, I couldn't see how those two statements are different.

When = Suff

Cloudy --> Snows

Only = Necessary
When = Suff

Cloudy --> Snows

That's how I see it, but reading your explanation it appears I'm wrong. With that said, I don't know why I'm wrong or how "the word of only changes the meaning of conditions."

Any clarification would be greatly appreciated

ALSO, and this may be a long shot, but is there a list on TLS of the indicators that goes beyond what the LR bible lists?

[timmydoeslsat]

We can change the language to something you are familiar with in everyday conversation.

I only drive my car when it is Wednesday.

What do we know if you drove your car? It must be Wednesday. Sometimes the "only when" phrase can be separated by other words in the sentence. The meaning is still the same though.

[naillsat]

It only snows when it is cloudy. Is this below understanding right:

snows --> cloudy ?

[dowu]

It only snows when it is cloudy. Is this below understanding right:

snows --> cloudy ?

Sounds right to me.

[SanDiegoJake]

It only snows when it is cloudy. Is this below understanding right:

snows --> cloudy ?

Sounds right to me.

It's right, but there's a bit of a grammar issue. Let's hit that grammar thing last though.

About necessary conditions and the words that introduce them: "Only if" (or the much less often used 'only when') should definitely be on that list. The way I think about conditionals with the words "only if" is to negate the action after the words "only if" and brain it out from there.

For instance: I read: "It snows only if it is cloudy." I think: What if it's not cloudy? I answer myself: Then it won't snow. I diagram: ~c --> ~s. I diagram the contrapositive: s --> c

Now for the technical grammar issue. The test writers won't misplace the modifier "only" as above. Grammatically, the sentence, "It only snows when it is cloudy" means that it only snows, i.e. it does nothing else. It doesn't rain. It doesn't hail. It doesn't sleet. It ONLY snows when it is cloudy. The LSAT will always get the grammar right, though, so it's not something you have to worry about. The "only if" has to be closest to the thing it's talking about (modifying).

Good luck!

[timmydoeslsat]

I absolutely agree about the possible grammar issue, but the LSAT expects one to be able to diagram the above statement in the way prescribed.