These words of JG Machen are clear and relevant to the present sad state of membership in evangelical churches.
In order, therefore, that the purity of the Church may be preserved, a confession of faith in Christ must be required of all those who would become Church members. But what kind of confession must it be? I for my part think that it ought to be not merely a verbal confession, but a credible confession. One of the very greatest evils of present-day religious life, it seems to me, is the reception into the Church of persons who merely repeat a form of words such as “I accept Christ as my personal Savior,” without giving the slightest evidence to show that they know what such words mean. As a consequence of this practice, hosts of persons are being received into the Church on the basis, as has been well said, of nothing more than a vague admiration for the moral character of Jesus, or else on the basis of a vague purpose of engaging in humanitarian work. One such person within the Church does more harm to the cause of Christ, I for my part believe, than ten such persons outside; and the whole practice ought to be radically changed. The truth is that the ecclesiastical currency in our day has been sadly debased; Church membership, as well as church office, no longer means what it ought to mean. In view of such a situation, we ought, I think, to have reality at least; instead of comforting ourselves with columns of church statistics, we ought to face the facts; we ought to recall this paper currency and get back to a standard of gold.
What is Faith? Pgs. 155-56.