Faith is confident to defeat doubt and unbelief. The reason is clear. Faith is confidence in God. Faith is assurance based upon the truth found in God's inspired word, the Bible. You see, faith comes by hearing, and hearing by the word of God (Romans 10:17). Faith gives you assurance, because you take God at His word.
Doubt can never be confident. No matter what doubt hears, there is never any certain assurance. Not only that, but doubt thinks no one else can really know that God is real. Doubt says, "Maybe God is real and maybe He's not. There are times I've thought He is, then again I think He's not." Doubt thinks those who say they believe in God are really just playing a religious game.
Unbelief is dogmatic. Unbelief says, "There is no God. It is ignorant and uneducated people who say they believe in God. How stupid. Show me the evidence. If there is a God, I would know it and understand." Unbelief lifts himself up in pride, looking down on others who believe.
Faith is confident in God, and you can be sure that God is at work in you. Faith is confidence with God our Father, and Jesus our Lord and Savior. Faith is confident in love, because God is love (1 John 4:8). Faith makes you confident with love, joy, and peace. Faith is confident through the Holy Spirit, and the fruit of the Spirit is love, joy, peace (Galatians 5:22).