In one sense the stages of bhakti are all developments of faith (sraddha) culminating in entering the “planets of faith,” as Pujyapada Sridhar Maharaja sometimes referred to as the paravyoma. Sri Jiva Goswamis writes that without ruci one cannot effectively engage in sasta-yukti, or properly reasoning about the import of scripture. He is saying the same thing as the Chandogya Upanisad but using the word ruci instead of sraddha: svalpapi rucir eva syad bhakti-tattvavabodhika. The implication of such statements is that logic alone will not unlock the door to understanding sastra‘s import.
So why are so many devotees unable to think clearly about the import of sastra? Is it lack of faith/ruci? I would say it is due to weak faith (komala sraddha) because sraddha implies faith in sastra—sastriya sraddha and the stronger one’s faith the greater one’s ability is to understand sastra. But other issues may also be at hand, such as aparadha.
I think the real test is not so much one’s ability or lack of ability to understand what one reads but one’s ability to change one’s thinking upon hearing the correct conclusions from a sadhu.
On the one hand you have those who can change their thinking with sadhu sanga and on the other you have those who are adamantly against the proper conclusion found in the context of sadhu sanga. Many fall somewhere in between these two extremes.
Faith in sastra really leads to faith in sadhus because sastra stresses this over and over again. Bhakti comes from bhakti in the context of sadhu sanga. Yet we find many with great faith in sastra (Prabhupada’s books only) and no faith in sadhus, but rather strong distrust of them. This is most unfortunate and a sign of weak faith in a dynamic sense of the term. Faith is understanding that removes doubt and confusion. To the extent that we don’t understand sastra‘s import we are not standing on a planet of faith.