"if" and "in case"

[Seiichi Myoga]

As for (1), Humberstone says in The Connectives that we can replace "if" with "in case" without much change in meaning.
And I know (1) actually means (3).

(1) If you're interested, Prof. Murgatroyd will speak tomorrow at five.
(2) In case you're interested, Prof. Murgatroyd will speak tomorrow at five.
(3) If you're interested, I inform you that Prof. Murgatroyd will speak tomorrow at five.

Then what Humberstone is really saying is that (2) means (3).
Am I right?

Thank you in advance
Seiichi MYOGA

[Dozy]

Without getting into hair-splitting analyses, (1) and (2) mean pretty much the same thing.

(3) is not a great sentence in my opinion. I think "in case" or "since" would work better here, depending on intended meaning.

[Seiichi Myoga]

Dear Dozy,

I appreciate your help and comments.

[Dozy]

I'm not sure that there is any difference in the acceptability of #3 (or any of the other sentences) between AmE and other varieties of English. I think it's probably more down to individual preferences. In #3 I tend to read "I inform you" as being conditional on "if you're interested", which then contradicts the fact that the speaker is informing the other person regardless. I know that actually, as in #1, "if you're interested" is not intended to directly condition anything else stated in the sentence, but still it feels a bit awkward to me.

4b should be "I'd like to inform you that". That fixed, I find 4a and 4b more satisfactory because it's fine to do something "in case" of something else without knowing whether that thing will be true or not. In fact, that's the whole point of "in case". 4b is a bit less abrupt than 4a, and would usually be preferable.

[E2e4]

From sentence "In case you're interested in it, I inform you that Prof. Murgatroyd will speak tomorrow at five." my conclusion is that if you are not interested in it prof. Murgatroyd will not speak tomorrow at five.

My version

Prof. Murgatroyd will speak tomorrow at five. I inform you for you might be interested in it. Anyway, I've already booked two chairs in case you're coming.

Thanks

[Beeesneees]

Sorry E2, that's not correct.
_________________
Cheers m' dears!

[Seiichi Myoga]

Dear Dozy,

Again, I appreciate your help and comments.

I'm afraid I wrongly understood your comments.

[Dozy]

In neither (1) nor (2) is there a prominent sense that the sentence is a true conditional one. The "if" and "in case" clauses are more just figures of speech designed to explain the speaker's reason for imparting the information and make the sentence seem less bald and abrupt.

In full, (2) would be "In case you're interested in going, I'm telling you that Prof. Murgatroyd will speak tomorrow at five". As usual, "in case" means that the speaker does not know whether a certain thing is or will be true, but is doing something anyway because it will be beneficial if that thing is true.

Strictly speaking (1) is not a logical use of "if", but it is an accepted idiomatic use, and is understood to mean the same as (2). If you had to write a sentence with a strictly logical "if you're interested" condition then it would be something like "Prof. Murgatroyd will speak tomorrow at five, and, if you're interested, you might want to go". However, this translation is not normally necessary since the original "If you're interested, ..." is understood as an idiomatic pattern.

The reason why (3) does not work very well (in my opinion) seems at least partly that the insertion of "I inform you" disrupts this idiomatic pattern. (5) suffers less from this problem and seems a tolerable sentence to me. (Being fussy, one could say that "I'm telling you" has a hint of forcefulness that is slightly at odds with the rest of the sentence. However, this nit-pick is unrelated to your main question.)