Faith and belief are two different things. Faith is much greater than mere belief. While belief may arise from the operation and conviction of the mind, faith never can. Its place is in the soul, and it arises from the opening of the perceptions of the soul. No one can possess true faith unless their soul is awakened by the inflowing of the Divine Love. In Galatians 5:6 we read, “For in Christ Jesus neither circumcision nor uncircumcision has any value. The only thing that counts is faith expressing itself through love.”
Faith is a quality of the soul, and increases as the amount of the Divine Love increases. Without the Divine Love there can be no faith. So, when we pray to the Father to increase our faith, it is really a prayer for the increase of the Divine Love. And when we pray directly for the Divine Love, faith will increase as well with each new inflow of the Love.
As Jesus states, “Your prayers call from the Father a response that brings with it faith, and with this faith comes a knowledge of the existence of this Love in your own soul” (http://new-birth.net/tgrabjvol1/jesus42.htm). Or, as we read in the Bible, “faith is being sure of what we hope for and certain of what we do not see” (Hebrews 11:1). So true faith makes the knowledge of the Love in the soul so certain and palpable that no doubt will ever arise as to its reality.
So to recap, true faith is more than a belief and exists only in the soul. By contrast, belief arises from the conviction of the mind. Since faith is dependent on the Divine Love, prayer for more faith is really prayer for more Love.