The author of Hebrews dedicates a lengthy part of his letter to the topic of faith. He defines it in two ways that are quite familiar to us: First, it is the assurance of things hoped for, and the conviction of things not seen.
Conviction of things not seen simply stated is that faith “sees” the invisible reality that is all around us. One cannot prove the existence of God based on his five senses. One can only know that he exists by first believing that he exists. This conviction manifests itself through believer’s attitude and actions.
Faith is also the assurance of things hoped for. By assurance, the author is speaking of the words of God. When the Scriptures attest that God created the universe, then the believer can have full assurance in spite of the scientific evidence hurled at him.
The author continues in Hebrews 11:2, “For by it the people of old received their commendation.” By example, then, we learn that faith results in actions which are commended by God.
One of the stories mentioned in passing is David. When David fought Goliath he demonstrated his faith in God to both his fellow Israelites and to the Philistines. David did not kill Goliath with faith like a sword. Faith is not a magical power that if, one has enough, one can perform miracles. Instead, David says to Goliath, “This day the Lord will deliver you into my hand” (1 Sam 17:46).
David’s faith allowed him to “see” two things: 1) the presence of God in the battle, and 2) a dead Goliath. His conviction of these was so strong that it caused him to act accordingly with all assurance. Seeing is not believing. Rather, believing is seeing.