Q. What is the heart referred to [in the verse in the Upadesa Saram] where it is said "Abiding in the heart is the best karma, yoga, bhakti, and jnana?"
(loosely: action, divine union, devotion, and knowledge)
A. That which is the source of all, that in which all live, and that into which all finally merge, is the heart referred to.
Q. How can we conceive of such a heart?
A. Why should you conceive of anything? You have only to see where from the "I" springs.