[Zelandakh]

Just to point out that ergo is also a conjunction in addition to being an adverb. Also, I do not think gnasher's second example is a full sentence. Perhaps a better comparison would be to

Justin said we should play Ghestem. So it must be a good idea to do so.

This still sounds a little strange though. Starting the sentence with so just sounds wrong to me, unless perhaps you are using the link to make a new (third) point in the second half of the sentence. If I were trying to do this I would be more likely to use that instead of so though.

Justin said we should play Ghestem. That this must be a good idea is clear and therefore [so] I will play it in all my partnerships.

Justin said we should play Ghestem. Ergo it must be a good idea. Ergo I will play it in all my partnerships.

Justin said we should play Ghestem, so it must be a good idea which I will play in all my partnerships.

Does the second of these really not sound harsher and less flowing than the other two for readers? The first also has the (desired?) effect of deemphasising the link between what Justin said and how good the idea is. Heck we can add a fourth point too.

Justin said we should play Ghestem, so it must be a good idea. I am going to play it in all my partnerships which should greatly improve our results.

Justin said we should play Ghestem. Ergo it must be a good idea. Ergo I will play it in all my partnerships. Ergo our results should greatly improve.

The construction in the second sentence is fine in the maths classroom. In regular usage though I hope it is clear that it is generally poor English. It would be appropriate perhaps for a thread in the Expert forum that Justin or Mike wanted to troll, perhaps ending the post with: "Ergo, only a complete novice would ask such a ridiculous question in this forum". Or perhaps as Hans suggests, where you have made the biggest leap forward in bidding theory for the last 20 years which will revolutionise the game. For the most part though, such posts sound to me like they think their readers are stupid, either because it is obvious the poster thinks they know more, or because they are looking to make a big deal out of some (usually trivial) point, or just because the writer wants to appear intellectual.

In this case it is clear that Justin is using Case 1, whether consciously or not. This solution was obvious for him and using ergo has the effect of belittling the person he was debating with. He could have added a "Trivial" at the end for extra effect. In this respect the usage of the word was very effective here. That does not make me like it any more.

[JLOGIC]

Glad my english stood up under fire

[gnasher]

 JLOGIC, on 2012-May-15, 04:26, said:

Glad my english stood up under fire

Though it was at the cost of having your name inextricably linked with Ghestem in Google's databases. Sorry about that.

[han]

 JLOGIC, on 2012-May-14, 10:07, said:

Heh, I honestly never realized people dislike the word ergo. Yes, I could say thus rather than ergo for the same number of letters, I did not know that thus was considered a better word than ergo. Thus is never a word I use irl though I do type it sometimes for variety, thus sounds funny to me, I'd rather say therefore than thus if speaking. I still do not know what the objection is to ergo, why do you hate it so much han?

I would never use thus when speaking either. I also would never use ergo, and I don't think I've ever heard anybody say it out loud. The idea of saying ergo out loud is very strange to me, but then, I am not American.

[phil_20686]

 JLOGIC, on 2012-May-15, 04:26, said:

Glad my eEnglish stood up under fire

Oops

[TimG]

 han, on 2012-May-15, 05:16, said:

I would never use thus when speaking either. I also would never use ergo, and I don't think I've ever heard anybody say it out loud. The idea of saying ergo out loud is very strange to me, but then, I am not American.

I don't recall ever hearing anyone say ergo out loud, it is certainly not a common occurrence in my experience. I would expect to see it only in texts, and thus would think of it as somewhat pretentious, intentionally nerdy at the very least, if I heard someone verbalize it in any setting other than a math classroom.

[JLOGIC]

I didn't even know ergo was linked to math lol

[cherdano]

 JLOGIC, on 2012-May-15, 13:22, said:

I didn't even know ergo was linked to math lol

Neither did I...

[han]

I also have not seen it in mathematics.

[gnasher]

Everything is linked to mathematics.