Chapter 17 presents the doctrine of the perseverance of the saints, which holds that it is impossible for those effectually called to "fall away" from the state of grace or, in other words, lose their salvation. Chapter 18 states that believers can receive assurance of faith. This assurance is based on "the promises of salvation, the inward evidence of those graces unto which these promises are made, the testimony of the Spirit of adoption witnessing with our spirits that we are the children of God". The confession does not teach that assurance is instantaneous upon conversion; rather, it states that "a true believer may wait long, and conflict with many difficulties, before he be partaker of it".