But the natural man does not receive the things of the Spirit of God, for they are foolishness to him; nor can he know them, because they are spiritually discerned.
The Bible makes clear that the ultimate reality is not this physical, temporary universe, but a spiritual realm that is beyond human perception. Our senses can see, hear, touch, taste and smell physical things, but we cannot discern spiritual things.
Jesus said, “No one can come to Me unless the Father who sent Me draws him” (John 6:44; see also verse 65). Not everyone has been called to understand now. Only those who repent and are baptized and receive the Holy Spirit (Acts 2:38) can “receive” or welcome the things of the Spirit of God.
For more about how God draws people to Him, see the article “Many Are Called, but Few Are Chosen.”