"Only" - Necessary Condition

[JD180]

Hello,

I am having some trouble diagramming when seeing the word "only".

"Only manuscripts whose safety can be ensured during the restoration process will be restored."

I have a system where I replace "only" with "required" and I ask "what is required here?" And I see that it is required that the safety can be ensured. Thus, this is the necessary condition and restored is the sufficient condition.

Will this system always work or can you see if there are any issues that may arise due to the placement of the term "only" in the sentence?

Thank you

[Adam Tyson]

"Only" is indeed a classic necessary condition indicator, JD180 (great name, I like that power of positive thinking!), but you have to be careful about special cases like "the only," which we discuss in some detail in the LR Bible. For statements about "the only way" or "the only people" you will find that the necessary condition may not be the thing closest to those words in the stimulus.

"The only way to get a 180 is to practice a lot." - what is "the only way" that these words refer to? Practicing a lot. That means practicing a lot is necessary, and getting a 180 is sufficient.

"My brothers and sisters are the only ones I trust with my secrets." - Who are "the only ones"? My brothers and sisters, so they are necessary. If I trust someone with my secrets, then it must be one of my brothers and sisters.

"Only" is a common indicator, and you will see it by itself, or coupled with other words like "only if" and "only when" and "only after." In all of those cases you are looking at an indication of a necessary condition, and you should build your conditional diagram with the "only" element to the right of a conditional arrow.

Good work, keep at it!

[islandmike]

In the original example:

"Only manuscripts whose safety can be ensured during the restoration process will be restored."

Does this function like "The Only" - where "manuscripts whose safety can be ensured during the restoration process" would be the sufficient, and "will be restored" is the necessary?

[Rachael Wilkenfeld]

Good question, islandmike.

Your analysis isn't quite right though. Whenever I work with conditional reasoning, I find it helpful to think "what does the author think is REQUIRED here?" That question often guides my analysis of conditional questions.

In this case we have two elements. (1) Manuscripts whose safety can be ensured and (2) manuscripts are restored. Which is required? Is it saying that if the safety of the manuscript can be ensured, then it will definitely be restored? Or is it saying that if a manuscript is restored, then the safety must have been ensured? The necessary term here is the safety. The second order fits the logic of the original sentence better. If it's restored, then it's required that the safety has been ensured. We aren't necessarily restoring everything that we can restore safely. We are however making sure that everything we do restore can be restored safely.

Ultimately, it's the underlying relationship described in the statement that governs which is sufficient and which is necessary. You can easily write the example sentence in different ways, different orders, that all have the same logical meaning.

Only manuscripts whose safety can be ensured will be restored.
The only manuscripts restored are those whose safety can be ensured.

The two statements above have the exact same conditional logic. It's just a matter of phrasing.

Hope that helps!