To enter the Kingdom of God is an act of favour. No man comes to God by his own understanding. It is not an intellectual process. If it was, then the academics would enter the Kingdom of God first. That they do not is evident by what they say.
All people sin.
Mankind is without the Holy Spirit. Therefore, the human mind is at odds with God. The reason is that God's nature is conveyed through the Holy Spirit. Without the Holy Spirit, you are at odds with the law because you do not have God's nature. That nature is derived from God as the centre of goodness.