Here’s how it works. A person goes to the doctor to get a tuberculosis shot so as not to contract the deadly disease. The doctor, to prevent the patient from contracting the illness, actually injects him with a small dose of the virus itself. Strangely enough, a small dose of TB prevents one from contracting the full-blown disease. The shot serves to build up the patient’s immunity to it. The lesser prevents the greater, keeping one from acquiring the real thing.
This is precisely what happens to so many people spiritually. They receive a small dose of religion, but it only inoculates them, preventing them from receiving the one true reality—Jesus Christ. They come to church, read their Bible, pray, even shed tears, but are never born again. Through increased exposure to Christ, their resistance to the convicting work of the Holy Spirit is built up, thus hardening their hearts and keeping them from entering into a personal relationship with Jesus Christ.
Untold multitudes of people within the church today are just like this. They have been inoculated with the gospel but never “contract” the real thing. They have walked an aisle, prayed a prayer, signed a card, made a decision, and been baptized. They have joined the church, attended Sunday school, sung in the choir, given their money, even served in church leadership. But despite all this, they have never been converted to Jesus Christ.
Excerpt taken from Absolutely Sure, by Steven Lawson.