TOUGH Conditional Statement with Confusing Indicators HELP! Forum

[youknowryan]

The following is an odd statement, since what appears to be the necessary condition is the sufficient:

"We can only win this battle if we receive more supplies."

This diagrams like so:
win -> supplies
~supplies -> ~win

My issue is how does one get there? Using standard indicator words, would make this statement look like this:
supplies -> win
~win -> ~supplies

The other trick I use is rearranging the sentence to an "if...then" format, but again this yields 2 reasonable possibilities:
I. If we receive more supplies, then we can win this battle.
II. If we win this battle, then we received more supplies.

When I am not rushed, I would pick the second as superior, but in the heat of an LR section, I can easily see one picking the first option only to regret it later.

Would someone dissect this statement and give some rules as to its handling?

[magicman554]

The first "reasonable possibility" is missing the "only," which makes it incorrect. There's your problem.

[kcdc]

If there is a win, then there must be supplies.

so,

win -> supplies

[magicman554]

If there is a win, then there must be supplies.

so,

win -> supplies

Don't confuse OP.

OP, look for "only," "must," "cannot unless," and other related words/phrases when tracing necessary conditions. Look for "if" (without the "only") and related when tracing sufficient conditions.

[homestyle28]

If there is a win, then there must be supplies.

so,

win -> supplies

[youknowryan]

I get what the previous two posts are saying, my issue is this:

At a quick read, the statement looks like "supplies" are sufficient since "only" appears to modify win. How would one know to read the statement like this:

"We can win this battle only if we receive more supplies."

Here, the only is moved to make the "if" an "only if".

OR

"If we win this battle, then we received more supplies."

Here the "if" is moved to win, while the only is dropped completely.

How does one do this without changing the meaning of the sentence like this one? What's the rule?

[Nulli Secundus]

"We can only win this battle if we receive more supplies."

We take that only and put it here:

"We can win this battle only if we receive more supplies."

Now it becomes an "only if", which makes the formulation as shown.

win -> supplies

[youknowryan]

"We can only win this battle if we receive more supplies."

We take that only and put it here:

"We can win this battle only if we receive more supplies."

Now it becomes an "only if", which makes the formulation as shown.

win -> supplies

See my previous post, I got that. The question: when I see a form like this, is moving the only like you did always safe to do? The concern is running into a statement where doing that would change its meaning. See what I am getting at?

[Nulli Secundus]

Do not get confused by rules too much, you should be able to tell if moving something from one place to another changes meaning or not.

In the given example, "we can only win if bla bla" means there is only one way of winning the battle and thus moving only before if does not change the meaning.

[magicman554]

And by the way, "only" does not have to precede "if," as in the following example: "If we are to win the war, it will only be for the fact that we were well supplied."

You have to rephrase. Best way to look at necessary conditions is to do just that: think of the scenario abstractly, and find a relationship between things where one depends on the other. In this case, winning the war depends on being well-supplied, so being well supplied is the necessary condition.

[OnlyLivingBoyinNY]

If there is a win, then there must be supplies.

so,

win -> supplies

Don't confuse OP.

OP, look for "only," "must," "cannot unless," and other related words/phrases when tracing necessary conditions. Look for "if" (without the "only") and related when tracing sufficient conditions.

While I agree that learning the indicators (can only a if b) is important, kcdc's simplistic reasoning makes a lot of sense: without supplies, there is no win. So, supplies is necessary, and win is sufficient.