T. Austin-Sparks emphasizes the church's vocation as a prophetic instrument representing God's mind and purpose, highlighting the need for believers to see the fullness of God's revelation and to be willing to pay the price for it. He discusses the importance of being a testimony to the world, as seen in the prophetic role of individuals and the church as a whole, which must reflect God's extraordinary work. Sparks warns against complacency and the temptation to settle for a lesser experience of faith, urging believers to commit to a deeper relationship with God that transcends ordinary human efforts. He stresses that true success in ministry comes from God's intervention, not human ability, and challenges the church to embrace its costly calling as signs and wonders in the world.