Doctrine is taught not only by sermons, catechisms, and instructional talks, not only by printed books and audio-visual devices, but also by worship patterns (liturgies, both written and unwritten; hymns and songs) and by creeds, confessions, and declarations of councils and synods. It is learned by attending to these and buttressing them with personal and group Bible study.
By all these means Christians and congregations seek to assimilate, articulate, and apply what the apostles taught the first churches in Christ's name. Faithfulness to this heritage is the mark of sound doctrine—doctrine, that is, that promotes spiritual health. Deviations from our biblical heritage constitute false doctrine, which will at least stunt growth and at worst ruin souls completely. Christian doctrine is thus serious business, as serious as anything with which the church ever deals.
Doctrine is not just a bundle of the church's own ideas, thoughts, and dreams about God, but is a declaring of what God himself has shown and told us. Doctrine assumes that God uses his gift to us of language to communicate with us; that he is in fact the primary author of the Bible, its human writers being his empowered agents; and that these writers did their work under the guidance of the Holy Spirit.