After reading Bhagavad-gita one should promptly come to the conclusion of Bhagavad-gita: one should give up all other engagements and adopt the service of the Supreme Lord, Krsna, the Personality of Godhead. If one is convinced of this philosophy of life, that is faith. Now the development of that faith is the process of Krsna consciousness.

There are three divisions of Krsna conscious men. In the third class are those who have no faith. If they are engaged in devotional service officially, for some ulterior purpose, they cannot achieve the highest perfectional stage. Most probably they will slip, after some time. They may become engaged, but because they haven't complete conviction and faith, it is very difficult for them to continue in Krsna consciousness. We have practical experience in discharging our missionary activity that some people come and apply themselves to the Krsna consciousness with some hidden motive, and as soon as they are economically a little well-situated, they give up this process and take to their old ways again. It is only by faith that one can advance in Krsna consciousness. As far as the development of faith is concerned, one who is well versed in the literatures of devotional service and has attained the stage of firm faith is called a first-class person in Krsna consciousness. And in the second class are those who are not very advanced in understanding the devotional scriptures but who automatically have firm faith that Krsna bhakti or service to Krsna is the best course and so in good faith have taken it up. Thus they are superior to the third class who have neither perfect knowledge of the scriptures nor good faith but by association and simplicity are trying to follow. The third-class person in Krsna consciousness may fall down, but when one is in the second class or first class, he does not fall down. One in the first class will surely make progress and achieve the result at the end. As far as the third-class person in Krsna consciousness is concerned, although he has faith in the conviction that devotional service to Krsna is very good, he has no knowledge of Krsna through the scriptures like Srimad-Bhagavatam and Bhagavad-gita. Sometimes these third-class persons in Krsna consciousness have some tendency toward karma-yoga and jnana-yoga, and sometimes they are disturbed, but as soon as the infection of karma-yoga or jnana-yoga is vanquished, they become second-class or first-class persons in Krsna consciousness. Faith in Krsna is also divided into three stages and described in Srimad-Bhagavatam. First-class attachment, second-class attachment, and third-class attachment are also explained in Srimad-Bhagavatam in the Eleventh Canto. Those who have no faith even after hearing about Krsna and the excellence of devotional service, who think that it is simply eulogy, find the path very difficult, even if they are supposedly engaged in devotional service. For them there is very little hope in gaining perfection. Thus faith is very important in the discharge of devotional service.