What is faith? It is one of the most variously defined words in the world. In fact, there are so many different versions of what it is that it is clear if one is correct, many others are not. More importantly, what is the Scriptural definition? First and foremost, faith is faith in God (Hebrews 11:6) and not other things (Psalms 20:7; Isaiah 42:17). Also, faith is not against reason (Scripture gives reasons to believe; see 1 Corinthians 15:1-11), but against sight (2 Corinthians 5:7, Hebrews 1:1). We need to have faith to believe God's promises even if we do not currently possess them (Romans 4:18-21). Faith is therefore not faith in faith or a leap of faith into darkness, but reliance on God, whose truth we know.
We are also promised great things through faith the size of a mustard seed (Matthew 17:20), which is a seed known for its smallness. Now certainly, the presence of faith is relevant (Matthew 13:58), but the chief word for doubting in the New Testament is a strong word "to waver". It pictures someone actually fluctuating back and forth between two opinions (James 1:6-8), not someone who has an occasional doubt pass through their head. One example of God's graciousness, even when our faith is imperfect, is Acts 12:1-19. Herod Antipas puts to death James the son of Zebedee and throws Peter into prison. The church calls together a prayer meeting to petition God for Peter's release. So God sends an angel, who rescues Peter from prison. Then Peter goes to the house where they are praying for his freedom and knocks on the door. And when the maid runs into the gathering and tells them Peter is at the door, they do not believe her. It is only when Peter, after much knocking, is let in that they recognize it is really him. I am convinced God often does things for us in spite of our imperfect faith.
I am therefore convinced that faith is not a mental exercise; it is not a state of mind we work up; it is not an indefinable experience that flies in the face of reason. It is, rather, our imperfect reliance on the promises of God, even though we do not see them now. And if we have even a spark of a real faith, God will meet us there.