"My people are destroyed for lack of knowledge" (Hosea 4.6). So mourned the prophet Hosea. The glory of the gospel of Jesus Christ is that "all shall know [God], from the least to the greatest of them" (Heb. 8.11). Spiritual knowledge is open to all God's children today. It is therefore not only our duty but also our privilege to seek this knowledge. In the present volume, brother Watchman Nee attempts to help us to develop this spiritual knowledge. He points out the difference between mental knowledge and spiritual knowledge, shows the ways to the true knowledge of God as well as of ourselves, and explains the relationship between spiritual knowledge and the renewed mind.