One makes his advancement in Krsna consciousness by voluntarily giving up his attachment to material nature, or maya. Such renunciation is called tapasya. But we are not very willing to perform austerities without good reason; therefore any man with a good scientific and philosophical mind, like your good self, must first appreciate what transcendental knowledge is. If you get knowledge, automatically tapasya will follow, and then you make your advancement in spiritual life. So to get knowledge is the first item for anyone who is hoping to find the perfection of his life. Therefore I advise you to read our books daily as far as possible and try to understand the subject matter from different angles of vision by discussing it frequently with the devotees at the New York temple. In this way you will gradually become convinced, and by your sincere attitude and devotional service you will make progress.
Letter to Bob Cohen, 16 June, 1972