This is an exerpt from a book called "Readings in Vedic Literature" by Satsvarupa dasa Goswami published in 1977 by the Bhaktivedanta Book Trust.

  "In the late sixteenth century, with the advent of Krishna Caitanya, in Bengal, Ramanuja's and Madhva's philosophy of Vaisnavism (worship of Visnu, or Baghavan (God)) reached its climax. Caitanya's philosophy of acintya-bhedabheda-tattva completed the progression to devotional theism. Ramanuja had agreed with Sankara that the Absolute is one only, but had disagreed by affirming individual variety within that oneness.  Madhva had underscored the eternal duality of the Supreme and the jiva (the eternal, individual soul or spirit): he had maintained that the duality endures even after the liberation. Caitanya, in turn, specified that the Supreme and the jivas are "inconceivably, simultaneously one and different" (acintya-bheda-abheda).
In rejecting impersonalism, Caitanya said that it clouds the Vedic literature's meaning. He explained the direct meaning of the sastras (revealed scriptures) as devotion (bhakti) to Bhagavan Krishna. Thus, Caitanya made an unprecedented contribution. Here was the possibility of a devotional relationship between God and man."