The church in Sardis had a great reputation for being alive, but their inward reality was…different. This church was dead. They had an outward reputation of thriving, but they lacked the inward reality of being alive.
The seven letters at the beginning of Revelation have multiple layers of meaning. They speak to the actual churches of that day, individual churches of today, a personal application for us, and a correlation with church history. This letter corresponds to the period of church history known as the Protestant Reformation—which had name outwardly, but over time lost their inward reality.
But it didn’t begin this way for the church in Sardis, for the churches that call themselves Protestant, or for the churches and people to whom this applies today.