Another proof for the RPW, one less direct, is the principle of uniformity. The principle of uniformity, a medieval idea, teaches that because there is one God, one King, and one church there should be one form of worship. Western individualism detests this doctrine, but it is effective in controlling the RPW. All Christians, separated by culture and time, should feel comfortable in worship no matter what culture or time period they live. One can see why western individualism would despise a doctrine that makes one give up its modern identity. Most people would rather give up the catholicity of the church then their present-day principles of worship. This doctrine is argued from inferences of uniformity found in nature (Job 38:31-33, uniformity found in the heavens; Gen 8:22, John 4:35 uniformity in the season), and uniformity found in Old Testament rituals (Num 9:13, the command that the Passover be kept at the appointed time and appointed way; Ex 12:49, the command for one law to govern home born and stranger; Lev 1-7, rules on sacrifices, 1 Chron 23:26, Levite services; etc.). Those texts that call for unity over division implicitly back this doctrine as well (1 Cor 12:25; Titus 3:10).
What about the things in worship that are unique to a certain culture or time? There are objects in worship that seem neutral with no biblical evidence for or against like amplification. Can the church use amplification when doing so is not commanded in Scripture? Should the church worship in a house or out in a field? These are a few issues in worship not clarified in Scripture. The question is begged, “How can the church actually follow the RPW, when there are so many things found in worship not found in Scripture” and “ Should worship rid all 21st amenities to only resemble the culture and time of the 1st C.E.?” The distinction between circumstances and essences has the answer, Westminster Confession 1.6:
There are some circumstances about the worship of God, and government of the church, common to human actions and societies, which are to be ordered by the light of nature and Christian prudence, according to the general rules of the Word, which are always to be obeyed.
Not everything connected with worship is worship. For instance the shape of buildings, the length of service, sitting and other non-religious activities have no religious significance. These are circumstances. Anything that culture or wisdom can potentially change without affecting or effecting worship is a circumstance. Some things found in worship are just natural without any moral cultic overtones. Some things are physical circumstances that aid worship, which occur alongside other civil and religious actions done by men and are not part of worship. They do not contribute moral goodness or badness to the agent in performance. Some physical circumstances, however, become moral because God sanctifies it. For example, the seventh day of the week became the Lord’s Day because he sanctified it. Elements are those things that God has given spiritual significance to like prayer and the reading of Scripture. Circumstances are physical man-made things that surround worship like time or place. The RPW does allow practices as amplification to aid worship as long as the church realizes that these are only physical circumstances that could be taken away without effecting biblical worship. A pastor could remove the microphone and remain biblical, however, he could not remove the sermon and remain so. The church, therefore, should employ 21st amenities as a blessing, while recognizing them as mere circumstances that help and are not worship.
 Schaff, “The Creeds of Christendom,” 603.