Sri Chaitanya Mahaprabhu showed by his personal life the validity of the doctrines of devotion described in Srimad Bhagavata. Holding Achintya-Bheda-bheda or identity-in-difference to be the nature of the Ultimate Reality whom he called Sri Krishna, Chaitanya demonstrated how Bhakti is the sure way to higher spiritual development.
We cannot see outside what we are not inside. The universe is to us what the huge engine is to the miniature engine; and indication of any error in the tiny engine leads us to imagine trouble in the huge one.
-Swami Vivekananda