1 Corinthians 2

Paul teaches a single truth that the world does not understand -

"...we speak the wisdom of God in a mystery, even the hidden wisdom..." (New Testament | 1 Corinthians 2:7)

Merriam Webster dictionary defines mystery as -

"...a religious truth that one can know only by revelation..."

Paul then teaches how one may learn truth that comes only by revelation -

"...God hath revealed them unto us by his Spirit: for the Spirit searcheth all things, yea, the deep things of God." (New Testament | 1 Corinthians 2:10)

"...so the things of God knoweth no man, but the Spirit of God." (New Testament | 1 Corinthians 2:11)

"Now we have received...the spirit which is of God; that we might know the things that are freely given to us of God." (New Testament | 1 Corinthians 2:12)

The Spirit or the Holy Ghost is only given to those that diligently seek for -

"...the natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned." (New Testament | 1 Corinthians 2:14)

The promise is for anyone if -

"...ye would ask God, the Eternal Father, in the name of Christ, if these things are not true; and if ye shall ask with a sincere heart, with real intent, having faith in Christ, he will manifest the truth of it unto you, by the power of the Holy Ghost.
5 And by the power of the Holy Ghost ye may know the truth of all things." (Book of Mormon | Moroni 10:4 - 5)

That is something the world does not understand.