Devotion and faith go hand in hand. Only when a person has faith in his friend will he be devoted to him. The opposite also is true and will be true. But to have a faith or devotion the knowledge that the person and his friends have been close and their past tested by either of them is necessary for their being devoted to each other. So the increase in knowledge, faith and devotion is gradual.
Mere knowledge is of no use. When the rocket scientist has a full knowledge of the working of the rocket but not an equal amount of faith in its working, the rocket is a failure before it even takes off as no sensible pilot would be ready to travel in it.
Mere faith is the same case. Knowledge and devotion are the two sides of the same coin. Even if one side is not stamped or the value of the coin is not known the coin is useless to the person.
If the devotion and knowledge of the Lord and the seeker is not equal and is not one that is recognized in the mind of the seeker than the subtle Truth of the Vedas cannot be apprehended. The relationship of the Lord with His Bhaktas can be had from the Puranas, why even from the Bible. The nature of the seeker with his friends is best known by the seeker himself. If the relationship between the seeker and the Lord is not mature in knowledge and devotion it is difficult to proceed.
This is why a Guru is needed to feed in knowledge and to plant the seeds of devotion in the minds of the seeker to an equal degree. Hence the Puranas become valid for the seeker and shall remain so for one can understand the full import of the stories only under a clear knowledge and a purer state of mind which will occur with a continuous study.
