I came across the OPC church website today and was extremely interested, and encouraged that there are other churches out there which appear to adhere to the Word of God. From what I have read on the website, the church appears to have almost exactly similar beliefs to the church of which I am a member (The Free Presbyterian Church of Scotland).
I would, however, be interested to learn more about what the OPC believes regarding the regulative principle.
The position of the OPC on the Regulative Principle is set forth in our Confession of Faith, in general at I.6 and as applied to worship at XXI.1 (also Larger Catechism 108, 109 and the briefer parallel statements of the Shorter Catechism), and in our Directory for the Public Worship of God, II.1. I am sure you are well acquainted with the former, but the statement in the Directory for Worship is: "Since the Holy Scriptures are the only infallible rule of faith and practice, the principles of public worship must be derived from the Bible, and from no other source" (and the rest of Chapters II and III spell out the more particular principles of Scripture by which we would govern our worship).
At that formal level of confessional commitment, we are probably basically in agreement. But I venture to guess that your communion practices the exclusive use of Psalms for singing in public worship, whereas we allow for uninspired hymns and songs (as long as their texts agree with the Scriptures, which same rule we would apply to extemporaneous prayers and to sermons).
Even among our churches there is some variation in the understanding or interpretation and implementation of the Regulative Principle. But I am quite confident you would not find any of our congregations substituting drama, films or dialogues for the preaching of the Word, inventing unbiblical sacraments and ceremonies, using ritual incense, candles, crossings, depictions of deity, etc.
With regard to "holy days" (I know some staunch Presbyterian communions permit no recognition of such occasions as Christmas or Easter), I think mostbut not allof our churches will have music, Scriptures and sermons on nativity themes in December and on themes related to our Lord's last week before His crucifixion and through His resurrection in the Spring, not as a matter of conscience but as a matter of utility. We would understand this as having the warrant of Scripture (except for those among us who do not think it has the warrant of Scriptureand we have tacitly agreed to live together in peace with that difference).
What else may be of interest to you in terms of your question, I would not know without your being more specific. So I hope this has been of help and invite you to come back with further questions, if you wish.
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