"What we have received is not the spirit of the world, but the Spirit who is from God, so that we may understand what God has freely given us. This is what we speak, not in words taught us by human wisdom but in words taught by the Spirit, explaining spiritual realities with Spirit-taught words. The person without the Spirit does not accept the things that come from the Spirit of God but considers them foolishness, and cannot understand them because they are discerned only through the Spirit. The person with the Spirit makes judgments about all things, but such a person is not subject to merely human judgments, for,'Who has known the mind of the Lord so as to instruct him?' But we have the mind of Christ." -1 Corinthians 2:12-16
Who can explain spiritual realities except a spiritual being who lives in a fully spiritual world? We are spiritual beings living in flesh, but one day we will make the transition and then will be able to see clearly. Until then, God has not abandoned us to try to work out our own salvation alone. Instead, He put the very mind of Christ at work in us. The Spirit talks to us, interpreting the world through God's eyes, bestowing wisdom, and guiding our every step. However, to those who don't have the Spirit, it sounds insane. Jesus told His followers He would give them His flesh to eat and blood to drink, and many abandoned Him thinking it was too hard of a teaching. And yes, if you don't have the Holy Spirit in you then you would never know that Jesus was talking about us consuming His body, but actually meaning the consumption of His teachings eagerly would be our salvation (and later setting up communion as a symbol of this). Thank you God for bestowing this gift on us and for shedding light on spiritual matters so we can come to know you better.