"We have not received the spirit of the world but the Spirit who is from God, that we may understand what God has freely given us." NIV translation
The world and the spirit of self that controls it cannot help us to understand the things of God. The Spirit of God helps us to understand the salvation that He has given us and just what it means. Our knowledge does not save us but it helps us to understand the nature of God and to appreciate what has been given to us. This leads to worship in truth and in spirit.
"This is what we speak, not in words taught us by human wisdom but in words taught by the Spirit, expressing spiritual truths in spiritual words. The man without the Spirit does not accept the things that come from the Spirit of God, for they are foolishness to him, and he cannot understand them, because they are spiritually discerned." NIV translation
The Holy Spirit was sent to guide our every action and even our every thought. Those that do not have the Spirit cannot understand the things of God because they listen in the flesh.
"The spiritual man makes judgments about all things, but he himself is not subject to any man's judgment: 'For who has known the mind of the Lord that he may instruct him?' But we have the mind of Christ." NIV translation
All people make decisions (judgments) every day about all kinds of things. We (the spiritual man) make these decisions based on listening to the Holy Spirit. Paul quotes from the prophet Isaiah to remind us that wisdom in all situations comes from the Lord. We have that "mind of Christ" through the power of the Spirit and are able to make decisions that are pleasing to God.