If you have only had the substitute, and you are fully accustomed to the substitute – in your mind, it is the real thing. Then, when the real thing comes along, you either cannot understand what you are experiencing, or you reject the real thing – and say it is a substitute. That was happening wherever Paul travelled, especially here in Athens. The idols of the Greek pantheon are a poor, box pancake substitute for the real thing, Creator God. It was up to Paul, enabled by the Holy Spirit, to share with them, the real thing.