In the medieval documents you come across, you will frequently see the infinitive being used in conjunction with the accusative. This is called an accusative and infinitive clause, or an indirect statement, and is translated in a particular way.
You will often be able to spot an accusative and infinitive clause coming up from the type of verb which precedes it.
|to hear||audio, audire, audivi, auditum (4)|
|to say||dico, dicere, dixi, dictum (3)|
|to think||puto, putare, putavi, putatum (1)|
|to believe||credo, credere, credidi, creditum (3)|
|to know||scio, scire, scivi, scitum (4)|