I love what the Amplified version of the Bible says in an extended place of the word "faith," so often used in the Bible. It consistently says: "faith (the leaning of your entire personality on God in Christ in absolute trust and confidence in His power, wisdom and goodness)."
So many people today make the mistake of believing that faith is simply a mental cognition that Christ is real and that he really did die on the cross for their sins. Historians don't question whether Jesus really lived and breathed. All one has to do is visit Israel to see that this is very much a fact. James warns us sternly, "you believe there is one God. Good! Even the demons believe that - and shudder." Satan and all of hell believe Jesus is real. What is the difference between us and them? It is this: The enemy won't and/or can't submit to Christ. They choose not to follow Christ. This then is the simplicity of true faith - to put yourself under God. To make him your leader. God doesn't expect us to be perfect in ourselves and good works, otherwise he wouldn't have sent Christ. He knew we needed help, and he payed the ultimate price to make us holy when "in Christ." This leaning of our daily lives and everything that we are on God in Christ. This is faith.
Those that live as if faith is a mental cognition are like the crowd in Mark 5:24-34. "A large crowd followed and pressed around him (Jesus)." And one woman comes through that crowd, probably crawling, and touches just the itsy bitsy edge of Jesus' robe. "Immediately .. she felt in her body that she was freed from (years of) her suffering." Jesus realized power had gone out from him and asked around to find who had done it. Listen to his disciples - "you see the people crowding against you ... and yet you can ask who touched me." This is just it. Many are "pressing around Jesus," in a sense of mental cognition, going to church or mass, praying daily prayers or even studying the Word of God, but they have not yet through process or decision chosen to lean their whole selves on God in Christ. It's called surrender of self and sin to God's ways. Not in perfection, but in submission.