Without fuel there is no fire. Doubt is the fuel for learning, and later for faith. The moment there is a genuine doubt, the mind opens, and knowledge enters. With doubt one considers the possibility that something new is possible: this involves learning.
Without learning there can be no knowledge of truth, let alone faith in it. Oh how I despise the priests of religion who speak lovingly of "faith": they know not of what they speak. I tell you, without knowledge there can be no faith. One must know all about God before one can have faith in Him.
Studying is easy, to truly learn is difficult, and to act on what you have learnt is more difficult still.