What faith provides is an experience that reason can only indicate or describe : the 'divine glories' (divyanam vibhutanam) and 'unfathomable prowess' (vibhutervistaro) of Godhead. That is why the key shlokas of Canto X are numbers 40 and 42, specially 42 : 'What use to you is this parade of my powers ? Have faith in me; know I exist, and that I sustain the world'.
Connected with the shraddha (faith) is bhakti (devotion). Bhakti, because it is outgoing, is the very opposite of desire, which is in-growing and so, when faith and devotion join hands, compassion is born. 'My compassion like a glowing lamp of wisdom scatters the ignorant darkness' of anywho happily sing the glories of God.
Arjuna's problem is obvious. As a Kshatriya warrior, he is unfamiliar with the co-ordinates of bhakti, though he knows what shraddha is, since training in arms under a guru demands the strictest shraddha. The only way he can discover the meaning of bhakti is by asking what it is -- a very poor way -- as unhelpful as trying to experience the fragrance of a rose by looking up its definition in a dictionary.
Yet Krishna goes along with Arjuna's request for a 'narration' of his yoga-bibhuti. How Arjuna will get a taste of this bhakti nectar (amrita : non-death) will become clear as the narration continues. The ladder of reason is a prelude to the leap of faith and devotion.