Without a doubt, faith on God's part is a gift, the first gift. And on the part of the believer there is a beautiful and fundamental act of gratuity. It is free from man because to give that vital adhesion, the believer does not have empirical reasons or quieting reasons. In full darkness, he throws himself into the arms of the Father, whom he does not see, without having any other motive and security than his Word. There is much gratuity (and merit) on the part of man in the act of faith. And we repeat, it is the maximum act of love.
It is clear that adult faith is not primarily intellectual adherence to truths, doctrine and dogmas but a vital and compromising adherence to a person. It is about assuming a Person, and by that assuming the entire Word, which conditions and transforms the life of the believer.
The believer who surrenders jumps over the mental processes, over the problems, over formulas and content ..., and "reaches" God, and thus the Lord transforms into certainty.
The security that reasoning could not give, is given by the same One that is the Content of the faith, if it has been accepted through an "obsequious" and unconditional delivery. And so the psalmist will affirm that :
The night is not dark for you, The night is clear as day (Psalm 138)
Extracted from the book Sensing Your Hidden Presence by Fr Ignacio Larrañaga