The central message of this sermon is that faith is not about hoping or feeling, but about being certain and sure of what God has promised, even when it cannot be seen. Faith involves plugging into the promises of God, which are often invisible and unseen, and trusting in His character and word as absolute truth. The speaker argues that faith is a simple yet profound concept that rests on who God is, and that it requires a deep familiarity with Scripture to understand what one hopes for. The takeaway is that true faith involves embracing the promises of God as certain and sure, even when they contradict our physical senses or circumstances, and living by faith rather than sight. This central message advances the belief that God's word and promises are absolute truth, and that faith is a fundamental aspect of being a Christian.