Why do believers find the doctrine of Christ in them believable?
The indwelling Christ is believable to them because it is practical and experiential—they know it has happened. Scripture calls them the temple or dwelling place of God, with the Spirit of God dwelling in them, and repeated emphasis confirms this reality.
Les explains that just as a husband and wife come together and become one, Christ and this body of believers become one, totally integrated. He notes that not only are we in Christ, but He is in us. The world knows nothing of this and may think he is a kook, but for those who love and know the Word, it is as plain as day. It is so believable because it is practical and experiential; we know it has happened. Les points to 1 Corinthians 3:16, where it is expected that we know we are the temple or dwelling place of God and that the Spirit of God dwells in us. Since Christ is bodily at the Father's right hand and cannot leave that bodily, when we speak of Christ being in us, it has to be in the third person of the Trinity, the Holy Spirit. He also reads 1 Corinthians 6 and emphasizes that when Scripture repeats something in short order, it is emphasizing and making a point.