Hebrews 11:1 says "Now faith is the assurance of things hoped for, the conviction of things not seen."
Hebrews 11:6 says "And without faith it is impossible to please Him for whoever would draw near to God must believe that He exists and that He rewards those who seek Him."
This is what a believers faith should be like. We have never seen God yet we believe that there is one. Yet some days I have to admit I have wondered if God is real and what if we are wrong. But I know that is Satan trying to mess with my mind and trying to make me doubt my salvation. Trusting in an invisible God may sound crazy to some but I know He is real because of what I've seen Him do in my life and in others as well. His hand of protection has been with me throughout my life. Why should I doubt? That is foolish. My God is an awesome God and He is the Way, the Truth and the Life. No one comes to the Father but through Him as stated in John 14:6. Do you need any other passage of Scripture to make this any clearer? I certainly don't. Take that Satan! No one not even you can snatch me from God's hand.