assistance of the Holy Ghost
Aid by which God prevents the teaching Church from falling into error, failing in her mission or losing His direction.
In Christ's discourse to the Apostles at the Last Supper several passages occur which clearly imply this promise:
"I will ask the Father, and he shall give you another Paraclete, that He may abide with you for ever.
The spirit of truth. ..he shall abide with you and shall be in you...
But the Paraclete, the Holy Ghost, whom the Father will send in my name, he will teach you all things and .bring all things to your mind, whatsoever I shall have said to you." (John 14)
New Catholic Dictionary