Negating unless statements

[Sherry001]

Hello hello ;
I was wondering if you could please tell me how to negate "unless" conditional statements in assumption questions . Do I negate both sides ? Here is my attempt.


"People who attempt to diagnose their medical conditions are likely to do themselves more harm than good unless they reply exclusively on scientifically valid information" .


People who attempt to diagnose their medical conditions are NOT likely to do themselves more harm than good -> even if they do NOT rely exclusively on scientifically valid information .


Thanks very much !
Sherry

[Nikki Siclunov]

Hi Sherry,

As you know, "unless" is a necessary condition indicator. The proper negation of a conditional statement requires showing that the sufficient condition can occur even if the necessary condition does not occur, i.e. that the necessary condition is not, in fact, necessary.

For instance, a statement such as

Unless the package is sent by air, it will not arrive tomorrow (Arrive tomorrow Air)

negates to

The package may arrive tomorrow even if it is not sent by air.

Quite often, the logical opposite of a conditional statement is formed using the phrase even if. Note that even if is not, by itself, an indicator of a sufficient condition: it merely states that the absence of one condition does not preclude the other from occurring.

Re: the example you gave, the same rules apply. The original statement can be diagrammed as:

Avoid doing more harm than good Rely exclusively on scientifically valid information

The logical opposite would have to show that the necessary condition is not, in fact, necessary. In other words, you don't need to rely exclusively on scientifically valid information.

Hope this helps a bit!

[LSATmaniac2.0]

Dear Nikki,

I actually had the exact same question for the exact same problem, so I'm finding this extremely helpful. Can I ask for a clarification of the 'even if' concept?

What I mean is, can we delve into the relationship between the 2 terms a bit more. Using your example,

Unless the package is sent by air, it will not arrive tomorrow (Arrive tomorrow Air)

The package may arrive tomorrow even if it is not sent by air.

can I take it to mean that the "even if" totally breaks apart the logical chain here? So that there is no longer any relationship between the two? Meaning that all bets are off when it comes to the package. It can be sent by air or not and we won't know either way whether or not it will get here on time? Conversely, Whether or not it gets here on time, we cannot extrapolate any information about its method of getting here whatsoever.

More compactly:

If it gets here on time [we have no idea if it goes by air or not]
if it DOESN'T get here on time [we have no idea if it goes by air or not]
if it goes by air [we have no idea if it comes tomorrow or not]
if it DOESN'T go by air [we have no idea if it comes tomorrow or not]

If this is so, then does the same apply with the medical diagnosis question, meaning there is no longer a relationship between avoiding more harm than good and relying exclusively on scientifically valid information?

Avoid doing more harm than good Rely exclusively on scientifically valid information

Becomes:

Avoid doing more harm than good [we have no idea if the info they are relying on is valid]
DON'T avoid doing more harm than good [we have no idea what happens if the info they are relying on is valid]
Rely exclusively on scientifically valid information [we have no idea if they avoid doing more harm than good]
DON'T rely exclusively on scientifically valid information [we have no idea if they avoid doing more harm than good]

Any clarification/input/evaluation would be much appreciated.


Sincerely,
LSATmaniac2.0

P.S. I apologize to Sherry if I'm taking stealing her thread, but I hope she would benefit from such a discussion too.

[Adam Tyson]

Hey there "maniac", I'll chime in here to say that you appear to have it exactly right, and I like the way you put it when you say that "even if" breaks the chain and all bets are off. As Nikki was saying, you negate the conditional claim by showing that the necessary condition is no longer necessary.

Not much more to add, really - well done!

[LSATmaniac2.0]

Hey there "maniac", I'll chime in here to say that you appear to have it exactly right, and I like the way you put it when you say that "even if" breaks the chain and all bets are off. As Nikki was saying, you negate the conditional claim by showing that the necessary condition is no longer necessary.

Not much more to add, really - well done!

Dear Adam,

Thanks for the affirmation and the exhortation. Feel free to use that wording if you think it would help someone understand this in the future.

Another slight aside. I'm thinking about streamlining my process here a bit. Would it be accurate to say that in the question, the answer choice is really getting at/insinuating that there is indeed a connection between the likelihood of doing oneself harm and the use of scientifically valid information? Meaning, that the author assumes, "yes, there is a relationship here between likelihood of harm and reliance on scientific information."
And by denying his assertion, with my even if construction, I break apart the correlation.

Original if then statement:

NOT likely to do themselves more harm than good they rely exclusively on scientifically valid information

Even if statement:

NOT likely to do themselves more harm than good EVEN IF they DON'T rely exclusively on scientifically valid information

Assuming I'm still correct thus far, I'm thinking that I don't even need to actually characterize the author's if then assumption fully, meaning knowing what is sufficient or what is necessary. As long as I understood the answer to be insinuating a correlation between the two, the answer would be right, because denying that correlation, to say that even if, means that I totally break the chain apart anyway, regardless of what was sufficient and what was necessary. So I could have chosen B without spending the time actually diagramming this out. This assumes of course that it is the only answer choice that mentions this correlation. In this case, the others don't match up to the issue.

Any thoughts? If I'm not being clear enough, I'll try to clarify.

Thanks again.

Sincerely,
LSATmaniac

[Nikki Siclunov]

Hi LSATmaniac2.0,

You're absolutely correct in that you don't need to diagram the conditional propositions if you fully understand their relationship, and therefore know how to weaken it. That said, the author isn't suggesting a mere correlation between not doing yourself harm and the use of scientifically valid information: the relationship is much more absolute than that. You must rely exclusively on scientifically valid information in order to avoid harm. To weaken this conditional relationship, you need a counterexample where someone did just fine without relying exclusively on such information. For instance, if your friend Betty never got the flu after following her psychic's suggestion to eat garlic 3 times a day, that would be an example of someone avoiding harm without relying exclusively on scientifically valid information.

Again, you definitely don't need a diagram if you understand what's going on. Over-diagramming can do more harm than good

Thanks!