The Purity Principle, inspired by Srila Bhaktisiddhanta's poem Vaishnava Ke, includes a translation and commentary on the poem by Swami Bodhayan, President Acarya of the Gopinath Gaudiya Math. The book illuminates obstacles to pure devotion, and the magnanimous spiritual practices of Vaishnavism. With sublime qualities like humility and tolerance, one can chant the Lord's holy names purely and live a progressive, joyful life of service. This helps the sincere practitioner to follow a devotional path without distraction. With clarity, humility, and precision, Swami Bodhayan explains the most basic and also profound issues which, when understood, can inspire the student/reader to attain the confidence and focus needed to make steady progress on the path of bhakti.