https://www.youtube.com/watch?v=zMhOlxDaFCo
This, like the subjunctive, is a lengthy topic; all we will do here is give an overview.
Sciō aliquō locō esse sēminārium │ I know that there is a seminary (in / at) some place.
What Vincent uses here is an indirect statement.
There is a good example of this from the National Latin examination:
Marcus … dīcit ¦ duōs fūrēs esse in apodytēriō │Marcus says that two thieves are in the changing room.
“Two thieves are in the changing room.” │ direct statement; the actual word used by Marcus
Marcus says that two thieves are in the changing room. │ indirect statement also known in English as reported speech
In English and other languages, an indirect statement is introduced by a conjunction:
Engl: he says that …; Fr: il dit que ….; Gmn: er sagt, dass …; Russ: on govorit, chto ….
Late / Mediaeval Latin can introduce indirect statements in the same way with the use of quod – but Classical Latin cannot do this; CL uses a completely different, and – at first sight – odd construction known as the accusative-infinitive. In English, it is not entirely alien; there are examples, but the usage is very restricted mainly to expressions of opinion / belief but there may well be other examples found in older English literature:
I consider ¦ (i) him [direct object] (ii) to be [infinitive] a good man = I think ¦ that he is a good man.
I believe ¦ (i) her [direct object] (ii) to be [infinitive] wealthy = I believe ¦ that she is wealthy.
We hold ¦ (i) these truths [direct object] ¦ (ii) to be [infinitive] self-evident = We believe ¦ that these truths are self-evident.
These constructions can sound rather old-fashioned, but they do exist and, in Latin, the use extends to all expressions of indirect statement and thought:
[1] Marcus … dīcit ¦ (i) duōs fūrēs [direct object: accusative] (ii) esse [infinitive] in apodytēriō
> (very) literally: Marcus says ¦ (i) two thieves (ii) to be in the changing room
> Marcus says ¦ that two thieves are in the changing room.
Further examples:
[2] Sciō ¦ (i) eum [accusative] (ii) venīre [infinitive]
> literally: I know ¦ him to be coming
> I know ¦ that he is coming.
[3] Credō ¦ (i) tē [accusative] sapientem (ii) esse [infinitive]
> literally: I believe ¦ you to be wise
> I believe ¦ that you are wise.
[4] Magister dīcit ¦ (i) discipulōs [accusative] (ii) studēre [infinitive]
> literally: The teacher says ¦ (i) the pupils (ii) to be studying
> The teacher says ¦ that the pupils are studying.
Therefore, let’s go back to what Vincent said:
Sciō aliquō locō esse [infinitive] sēminārium [accusative]
> literally: I know ¦ a seminary to be in some place.
> I know ¦ that there is a seminary in some place.
At this stage simply be aware of this construction since there is much more involved in it.
