What do Ferdinand Demara, the church, and Belgic Confession Article 29 have in common? I’ll try to explain. Have you heard the name, Ferdinand Demara? He was perhaps the greatest imposter ever. He dropped out of high school, ran away, and became a monk. He went AWOL from the Army and Navy. As an imposter, he was a college instructor, prison warden, law student, and more. This part is really amazing. Demara stole a doctor’s credentials and posed as a Royal Canadian Navy surgeon. On one occasion, Demara extracted a bullet lodged near the heart of a wounded soldier. He used a medical textbook as his guide. He was eventually exposed as a fraud. 
We should differentiate between the visible and invisible church. The visible church is exactly that, visible. You can see it. The visible church is composed of all those who outwardly confess Christ and their covenant children. And within the visible church are imposters like Ferdinand Demara. Though in many cases imperceptible, imposters coexist with true believers in the visible church. The invisible church, on the other hand, is composed of all true believers. Scripture calls them the elect.
Think about God’s covenant of grace. Pre-incarnation, the covenant of grace was administered to God’s covenant people (infants included) by “promises, prophecies, sacrifices, circumcision, the paschal lamb, and other types and ordinances delivered to the people of the Jews, all pointing to Christ to come.”  There were imposters among God’s covenant people, yet they were external participants in the covenant of grace; they received gracious gifts from God within the church, yet they never truly believed. Today, post-resurrection, the covenant of grace is administered to God’s covenant people (infants are still included) by the preaching of the law and gospel and the administration of the sacraments. Same covenant of grace, different administration. There are still imposters among God’s covenant people who are external participants of the covenant of grace. They hear the Word and receive the sacraments, but not unto their blessing, rather, unto their condemnation because they do not truly believe. Only those members of the invisible church, internal recipients of God’s covenant of grace in Christ, those who receive the Word and sacraments by faith, truly benefit and receive the grace promised in the Word and sacraments. No faith, no benefits. True faith, true reception of grace. The point is, all those in the visible church receive God’s means of grace, yet only the invisible church, only internal participants (faith) of the covenant of grace, actually receive God’s grace.
Here’s where Belgic Confession Article 29 comes in. It says as we heard last week:
We are not speaking here of the company of hypocrites who are mixed among the good in the church and who nonetheless are not part of it, even though they are physically there. But we are speaking of distinguishing the body and fellowship of the true church from all sects that call themselves “the church.” 
Okay, when we think about the marks of the true church, we’re not talking about the imposters mixed in with true believers in the visible church. People can belong to the visible kingdom of Christ in the church while not actually belonging to Christ himself. That’s to be expected as Scripture reveals. Article 29 teaches us how to distinguish between the true church and the false church.
Think about all the different groups that call themselves “the church.” Roman, Lutheran, Reformed, Presbyterian, Anabaptist, Anglican, Methodist, and more.  This is what Article 29 means by “all sects.” They all claim to be “the church.” How do we know they are the true church and not a spinoff, cult, or false church? False churches are groups of people who confess Christ but hold to doctrines and practices which deviate from Scripture (rightly interpreted). A true church is so much more than a body of people declaring themselves a church.
For example, in San Francisco, CA there is a group of people who call themselves herchurch. They worship at 10:30 am on Sundays. They are part of the Evangelical Lutheran Church in America (ELCA). And they worship goddesses together. They sing worship songs containing lyrics like, “Our Mother who is within us, we celebrate your many names.” They celebrate LGBTQIA+ ideology, and their former Associate Pastor is transgender. Are they a church because they self-identify as one? Matt Walsh asks the question, “What is a woman?” I’d like to ask: What is a church?
Herchurch is an extreme example but within evangelical Christianity in America and the world, many false churches, from big assemblies to home groups, simply masquerade under the guise of “church.”
Dear listeners, how can you tell if you belong to a true church? How should you begin to think through that question? I think many people take such pride in being Lutheran, Presbyterian, Methodist, etc. that they care more about their affiliation with their chosen sect or local church than they do about the marks of a true church and whether they belong to a true church. In these cases, loyalty can be a façade for idolatry and unbelief.
And how do we know what a true church is when so many local churches claim to be Bible-believing? Daniel Hyde gave us something helpful to consider in his book With Heart and Mouth. He wrote:
[All] these multitudes of churches say that they follow the Bible, are Christian, and practice biblical Christianity. The wisdom of the day in finding a church is that you should attend a “Bible-believing church.” The problem is that everyone describes his local church this way. Christians are taught that they can choose a church based on their personal preference. Some like traditional churches, while some like contemporary; some like one kind, and some like another. We are told that whichever church best serves the needs of a family is the church one should attend. 
I think Daniel is exactly right, and this is sad because as many people choose a local church, they choose according to their preferences and not according to God’s Word. Many people never stop to ask, “Is this a true and faithful church? Is this a local church that bears the marks of a true church?” Instead, they just look for a busy youth group, social outreach, a great band, or the like. They’d do much better choosing a church based on the marks of a true church.
If there is one thing we need in evangelical Christianity in America it is this: the discernment to tell a true church from a false church. We need to know the marks of a true church, and we need to belong to a true church for our temporal and eternal well-being.
So, next time let’s begin to unpack the marks of a true church in order to belong to one in order to receive God’s means of grace for our eternal good and in order to best love God and our neighbor.
 The Confessions of Our Faith, Fortress Edition, ed. Rev. Brian W. Kinney (Fortress Book Service & Publishers, 2007), 13.
 Daniel Hyde, With Heart and Mouth: An Exposition of the Belgic Confession (Grandville: Reformed Fellowship, Inc., 2008), 390-391.
 Ibid., 392.
Quotes from the Heidelberg Catechism are taken from Zacharias Ursinus & Jonathan Shirk, The Heidelberg Catechism (Manheim: Small Town Theologian, 2021).
Scripture quotations are from the ESV® Bible (The Holy Bible, English Standard Version®), copyright © 2001 by Crossway, a publishing ministry of Good News Publishers. Used by permission. All rights reserved. May not copy or download more than 500 consecutive verses of the ESV Bible or more than one half of any book of the ESV Bible.