In the following quote from the great Scottish Reformer, John Knox, we see how vitally important the maintenance of the three marks of the Church are to its role, and for that matter to the witness of Christ in the world. The three marks constitute the ‘face’ of the Visible Church. That face of the Church, which identifies and distinguishes it among others, is the very face of Christ among men. So to the degree that the marks are compromised, the face of the Church and so of Christ are compromised. And where the marks are absent, the Visible Church is absent – and Christ walks not among such snuffed-out candlesticks.
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“The notes of the true Kirk are three: Word, sacraments and discipline: first, the true preaching of the Word of God in which God has revealed himself unto us; second, the right administration of the sacraments of Christ Jesus, which are annexed to the Word and promise of God to seal and confirm them in our hearts; last ecclesiastical discipline uprightly administered, as God’s Word prescribes, whereby vice is repressed and virtue nourished. In the observation of these notes the true face of Jesus Christ appears. We cannot make the face of Jesus Christ appear. Nevertheless, Jesus Christ himself, made known through Word and sacraments, is the true ordinance governing the life, form, and activity of the Church. We believe in Christ in the midst of those who meet in his name and by faith hear the voice of his Spirit speaking in and through the Scriptures and obey him. We see him in the Sacraments, and walk in holiness according to the leading of the Spirit of Jesus Christ. There the true Church manifests itself in the power of the presence of Christ the sole Head and Lord of the Church – there it steps forth before us, and distinguishes itself from any Church that usurps his authority.”