The Institutes opens with a sentence that frames everything after it: nearly all our wisdom consists of two parts, knowledge of God and knowledge of ourselves, and each entails the other. From that double knowledge Calvin builds his account of a God majestic and self-revealing, known truly though not exhaustively in Scripture, whose word is confirmed in the believer not by the church's authority but by the internal testimony of the Holy Spirit, one of the book's most influential moves. Human beings, created good and fallen totally, cannot ascend to God, so God descends: the second book traces redemption through the law and the covenant to Christ, whom Calvin presents in the threefold office of prophet, priest and king. The third book, the longest, describes the Spirit uniting believers to Christ through faith, and treats justification by faith alone, sanctification, prayer, and, placed deliberately late as a pastoral doctrine rather than a speculative first principle, predestination, God's eternal election of some to life.
The fourth book gives the Reformed doctrine of the church, its ministry and discipline, reduces the sacraments to baptism and the Supper, in which Christ is received truly though spiritually, and ends with civil government, honoured as God's ordinance yet bounded, since obedience to rulers must never become disobedience to God.