Read Chapter 29(THE MARKS OF THE TRUE AND THE FALSE CHURCH) of the Belgic Confession

We believe that we ought to discern diligently and very carefully from the Word of God what is the true church, for all sects which are in the world today claim for themselves the name of church.1We are not speaking here of the hypocrites, who are mixed in the church along with the good and yet are not part of the church, although they are outwardly in it.2We are speaking of the body and the communion of the true church which must be distinguished from all sects that call themselves the church.The true church is to be recognized by the following marks: It practises the pure preaching of the gospel.3It maintains the pure administration of the sacraments as Christ instituted them.4It exercises church discipline for correcting and punishing sins.5In short, it governs itself according to the pure Word of God,6rejecting all things contrary to it7and regarding Jesus Christ as the only Head.8Hereby the true church can certainly be known and no one has the right to separate from it.

Those who are of the church may be recognized by the marks of Christians. They believe in Jesus Christ the only Saviour,99flee from sin and pursue righteousness,10love the true God and their neighbour11without turning to the right or left, and crucify their flesh and its works.12Although great weakness remains in them, they fight against it by the Spirit all the days of their life.13They appeal constantly to the blood, suffering, death, and obedience of Jesus Christ, in whom they have forgiveness of their sins through faith in Him.14

The false church assigns more authority to itself and its ordinances than to the Word of God. It does not want to submit itself to the yoke of Christ.15It does not administer the sacraments as Christ commanded in His Word, but adds to them and subtracts from them as it pleases. It bases itself more on men than on Jesus Christ. It persecutes those who live holy lives according to the Word of God and who rebuke the false church for its sins, greed, and idolatries.16

These two churches are easily recognized and distinguished from each other.