The book of hebrew best define faith as ; the substance of things hoped for, the evidence of things not seen. It went further to mention people of the old who lived in faith in their walk with God. The matter of faith has become more difficult with each generation especially when it seems as if God no longer hears us. The faith of many grew cold at one point when it seemed as if their prayers were carried away by the wind and wicked men prospered over the righteous. Habakkuk, a prophet, saw the need to cry and question his faith, nothing seemed to work as it should and after much debate, and questioning, he came to the conclusion that the righteous can only live by faith.
This message of faith is crucial to this age, an era where wickedness seems to increase on a daily basis and our prayers look as if it's falling on deaf ears. The righteous at one point are losing trust in God and are adopting what the world celebrates. One thing I learned is that the devil desires us to come to this point when things seem to fail, not just to test our faith but to make us lose this weapon of war(faith) in our spiritual warfare.
To walk with God, we need to put in the armor of faith because it's by faith that we see God in everything. The "just" doesn't walk with sight else he does lose trust in that which holds more value. The "just" walk by faith, the substance of things hoped for, these are the things God had promised us, what he had said would come to pass in our lives, they are not things we see at the moment but his words stand as the substance of that thing we hope for. So they are not vain faith, but faith in the word which God has made known to us.