Peter Brandon emphasizes the significance of being a spirit-filled assembly, distinguishing between merely gathering as a church and experiencing the true presence and power of God among His people. He highlights that a church can appear to be a New Testament assembly yet be spiritually dead, stressing the necessity of a living encounter with God for genuine evangelism. Brandon draws from Acts 2 to illustrate how the Holy Spirit filled the early believers, enabling them to speak in tongues and effectively spread the gospel, and he calls for a return to first love and the authentic power of the Spirit in today's churches. He warns against materialism and the loss of spiritual fervor, urging believers to seek the presence of God and the manifestation of His power in their gatherings.