To understand the development of doctrine, it is necessary to understand two concepts:
Progressive revelation and how the church developed its theology.
Progressive revelation means that God worked over time, with different persons and through different means, to reveal Himself and His truth in the Bible. A clear indication of this in Scripture is found in Heb. 1: 1-3 as well as 1 Pet. 1:10-12. Because of this, we often weight the later portions of Scripture more heavily regarding doctrine, for they provide the fuller explanation of many teachings. However, later biblical writers sometimes presuppose certain well-developed knowledge on the part of their readers and so do not state the assumed knowledge. In such cases, earlier portions of Scripture may give us a fuller understanding of certain aspects of doctrine.
Theological development in the church has been necessary because of the occasional and non systematic nature of the New Testament writings. The Bible contains enough truth for the establishment of clear, coherent doctrine, but it rarely presents that truth in a systematic teaching. Therefore, the people in the church have necessarily and appropriately contributed thought and organization as the truths of the Bible have been expressed and extended within their own historical and intellectual setting.