Batteries in the Flashlight
How can you tell the Holy Spirit is present?
It is just like batteries in a flashlight. You can't tell the flashlight has batteries in it until you try to turn it on. When it is turned on you know if there are batteries or not.
With the Christian life, if the Holy Spirit is present the Christian shines brightly with the life that Christ wanted us to live. If a person does not have the Holy Spirit, they will not shine.