The right of testing the Master through critical reasoning has always been conceded to the disciples. But if, after testing and being satisfied about the Perfection of the Master, a disciple shows any wavering of faith, it is a result of a deplorable deficiency in his sincerity of approach and integrity of purpose. As there is much uncritical and undeserved credulity given to claimants of spiritual wisdom, so there is much unjustified wavering of faith in spite of a convincing basis for it in one’s own experience. Just as uncritical credulity is ultimately the result of then conscious operation of many worldly wants, unjustified wavering of faith is also due to the unconscious operation of desires that run contrary to the effective manifestation of a rationalized faith. In the first case desire is the source of unwarranted belief, and in the second case desire is the source of unwarranted doubt. Cravings have a tendency to pervert the functioning of critical reason. An unwavering faith grounded in pure intuition can come only to a mind that is free from the pressure of diverse wants.
True faith is therefore a matter of gradual growth. It grows in proportion to the success that the disciple attains in freeing his consciousness from diverse cravings.
-Discourses 7th Ed. p367