Understanding anything requires an open mind which is willing to ask simple questions.  Paul was explaining that God's logic and wisdom was different from the corrupted wisdom of the world, so he asked, "Who knows what somebody is thinking?"  The obvious answer is – only the person who is thinking.  In the same way, nobody can know what God is thinking, except God.

Only the Spirit of God has full knowledge of the deepest thoughts of God the Father and God the Son (John 14:26).  We cannot, with any integrity, make up or imagine what God is thinking, but the Spirit knows and He has revealed it.  He inspired about forty authors, including the apostle, to write the Scriptures (2 Peter 1:20-21).  The most important revelation is about God's salvation plan and how to interact with Him.

Salvation through faith in Jesus, who died to pay the penalty of the sins of the world, was uniquely God's idea.  We could never have invented that plan through human logic (which cannot see weakness as a route to glory).  The Spirit not only spoke to us through His messengers, but when we believed in Christ He also came to us … to live in us.  So God has given us more than a message; He has given us Himself to continue to reveal to us what pleases God and how to live for Him (John 14:16).  

And yet believers are often drawn back into thinking that the world has the answers.  We are tempted to think that God is not sufficiently up to date or that His Word needs to be modified to suit the corrupt ways of the world.  It is a spiritually deadly lure.  Wise Christians recognise that human thinking is dangerously limited and will rob the believer of the peace and joy of believing.  So invest more in God's Word, so that you will learn to love God's wisdom and be able to see that worldly wisdom can never have the last word.  Living God's way will cause your colleagues at work and friends in the community to ask, "Why?".  Tell them about the gospel of Jesus and why you love Him.  It will strengthen your faith and perhaps ignite theirs.