15.8.3.1 Infinitivanschluss bei Subjektgleichheit, Akkusativ- und Dativeobjekt

Basically there are always two options how to describe a second action within a phrase. Either with an infinitive or with a phrase starting with a conjunction, like 'that'.

Examples
  He admits to be wrong.
Il admet s' être trompé.
  He admits that he is wrong.
Il admet qu' il s' est trompé.

However, it is only possible to use the infinitive, if the subject is the same or if there is an object that functions as subject for the second phrase. If there are different subjects and no object (or none that can function as subject for the second phrase), then the phrase needs to be splittet. This works independently whether there is no preposition or any of the mentioned prepositions.

Example without objects
Il admet qu' ils se sont trompés.
  He admits that he is wrong.
Il aime nager.
  He likes to swim.
Il aime qu' ils nagent.
  He likes that they swim.
Il dit avoir été trompé.
  He says to be cheated.
Il dit qu' on les a trompés.
  He says that one has cheated him.

If there is an object (direct or indirect) then these can function as subject for the infinitive and therefore here it is not necessary to construct the sentence with que.

Examples with objects
Il invite tout le monde à participer à ce processus. (tout le monde is subject for participer)
He invites everybody to participate in this process.
Je l' ai empêché(e) de raconter des bêtises. (le / la is subject of raconter)
I have prevented him from telling nonsense.
Il l' a aidé(e) à réssoudre ce problème. (le / la is subject of ressoudre)
  He has helped him to solve this problem.
Il l' a prié(e) de ne pas le lui dire. (le / la is subject of dire)
  He asked him not to tell him.

There is another issue about the infinitive - the time it can describe. Infinitive constructions can only describe something in the same time as the teller is (present) or something from the past. This is not different from English, however, we wanted to mention it at least.

Examples
Il croit ne pas avoir reçu assez d' argent.
  He does not believe to have received enough money. (past)
Il croit ne pas recevoir assez d' argent.
He does not believe to receive enough money. (present)
but: Il croit qu' il ne recevra pas assez d' argent.
  He does not believe that he will receive enough money. (future => no infinitive construction)






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