Pure and Less Pure churches
IV. This catholic Church has been sometimes more, sometimes less visible. And particular Churches, which are members thereof, are more or less pure, according as the doctrine of the Gospel is taught and embraced, ordinances administered, and public worship performed more or less purely in them.
V. The purest Churches under heaven are subject both to mixture and error; and some have so degenerated, as to become no Churches of Christ, but synagogues of Satan. Nevertheless, there shall be always a Church on earth to worship God according to His will.
(Westminster Confession of Faith 25.4-5)
The church is created by the Word of God. Yet it consists of sinful humans, we who still retain the old sinful nature within us. What do you get when a bunch of sinners come together? They sin of course. Sin is not just about external morality but it includes other things like pride and arrogance, and thus even the good things and virtues we have including our intellects can be used to sin against God and against each other.
The ideal for a church, as the Body of Christ, called by Him and instituted by Him, is holiness. That is what the church is called to be. But sin is ever present in her members, and thus the church is not subjectively holy. How many times have believers been hurt by someone within the church? Probably quite often I would imagine. Even with the best of intentions, our words may be said intemperately causing hurt instead of comfort to the ones receiving them. Thus, the church struggles with sin in her members, some more than others.
It is this reality that the Reformed faith acknowledges, in speaking of the pure and the less pure church. Among true churches, some believers in some churches are obviously more godly and kinder than others, and some are better in preserving orthodoxy than others. All of them are true churches, yet they vary in how pure they truly are. But since we are not saved by works, so therefore there is nothing wrong with churches falling on a spectrum as believers individually work out their own sanctification processes in varying degrees in various churches.
The introduction of the spectrum between pure and less churches should help us move away from an ideal and unrealistic view of the church. There are indeed true and false churches, but if we stick to only this distinction, then there is a real temptation for a believer to see struggles with sin in his church as evidence that his church is a false church, instead of a true church that is struggling with sin.
Therefore, the Reformed church does not substitute the new law of Rome (complete with her sacerdotal office and seven sacraments) with another set of "law" (full adherence to purity of doctrine and practice). Rather, while the marks of the true church are indeed marks of the true church, progressive sanctification in the life of believers and in the life of a church is recognized. The ideal is for us to strive towards, while recognizing the reality of sin among believers.
The idea that there is the true and the false church, while among the true churches there are purer and less pure churches, is helpful to us in this time where many different churches abound. There is a truism that states "there is no perfect church" and that is certainly true. No church is perfect and made up of perfect people. In this sense, when we are disappointed with people in the church, it is "normal." There is no need to denounce the church and leave her, since you are just as much a sinner as the one who offended you. When there is conflict in the church, we should aim for reconciliation and forgiveness, not revenge. There is no perfect church and one should not expect there to be a perfect church. Struggle instead with living lives with others who will definitely hurt and offend you just as much as you will do the same to them. Learn to forgive others just as Christ forgive you (Mt. 6:12).
At the same time, while it is true that no church is perfect, there is a wrong way to interpret that, which is to use it to deny the distinction between the true and the false church. The truism could be abused to allow heresy into the church and to keep people in a church that teaches heresy. Here is one place where Reformed churches would disagree with the current Evangelical mindset, where believers think they should stay in false churches in an attempt to change her from the inside. But what does Scripture teach? "Go out from their midst, and be separate from them" (2 Cor. 6:17 c.f. Is. 52:11). We are not to think we can subvert (for that is what it is) a false church from the inside, but rather believers should always join true churches and undertake evangelism of false churches from the outside.