Because it’s obvious to me that His Spirit is intimately involved in preservation of unity.
When Paul wrote to Colossae, Christ was in the saints – though it was a mystery.
His Spirit was in the prophets before He was born among men, when they sought the details of that incarnation to serve those who would follow them.
His Spirit was in David, who begged that the Spirit not be taken away from him when he sinned against God.
It was His prayer to be in us.
If His Spirit isn’t in us, we aren’t His.
His Spirit is how He seals us as His own, and guarantees what He has promised later.
His Spirit is how He strengthens us from within.
His Spirit is how God pours out His love into our hearts.
Our bodies are His temple.
So it’s a question more important than whether the Spirit works apart from the Word or how He works or whether He still works today. Because if He dwells in followers of the Word throughout Christians’ lives, it’s inconceivable that He could be a freeloading parasite, sponging off of the prophets of His book. It’s a question more important than how can we know He is in us, because He said He would be and when God says He’ll do something, it’s as good as done. It’s more important than any question raised by the advertisers of GatorAde because it has to do with the water of life, the Spirit of God, the hope of glory:
Is He in you?