Basic Christianity, grounded in the purity of relationship with Jesus will confound and turn the heads of the lost world unlike any crafted religious doctrine theologians could possibly hope to design by their own intelligence based on biblical knowledge alone. The power of God works through the simplest of His children, meek and humble, while the most astute theologian may look on with indignation, mentally concluding that such simplicity could never make a dynamic and lasting impact on the lost.
Since a relationship with the Father is based on the manifestation of His Spirit embraced by those He loves, then the fruit of the Spirit is the evidence of that intimacy. For it is not by might, nor by power, but by His Spirit, through those whom He knows and is well pleased with. Through them, will be displayed the only life changing power that will pierce and expose the depths of the underlying darkness of humanity that keeps the world bound in depravity. It is the only power that makes a decisive and permanent change in a person's life.
Doctrine is crucial, but it can not be merely learned. It must be lived.
"At that time Jesus declared, 'I thank you, Father, Lord of heaven and earth, that you have hidden these things from the wise and understanding and revealed them to little children; yes, Father, for such was your gracious will.'" (Matthew 11:25, 26)