Ramanuja was a great Vaishnavite philosopher and social reformer. He was born in the year 1017. He is revered and held in very high esteem by the entire Vaishnavite community.
He resurrected Vishisht Advaita and followed the path of great Vaishnavite leaders like Nammalwar, Nadamuni and Alawandar. Adi Sankara, the founder of Advaita philosophy, revived Hinduism at a time when Buddhism was on the ascendant.
Sankara’s philosophy is based on the following verses of the Vedas: Prajananam Brahma from the Rig Veda, Aham Brahmasmi from the Yajurveda, Tat Tvam Asi (You Are That) from the Samaveda, and Ayam Atma Brahma from the Atharva Veda. Advaita believes that the individual self, or atman, is not different from the universal self, or Brahman. Man is not different from God.
This is also based on the Mandukya Upanishad commentary by Sage Gaudapada. Advaita also explains the Vedic concepts of nirguna and niranjana to describe God as being attributeless.
Ramanuja, however, did not accept these explanations. His argument was that if we were Brahman, why should we undergo suffering in this world? Ramanuja said that due to the great quality of saushilya and vatsalya, God is so fond of and protective towards His devotees that He goes to any extent to please them.
This quality of the Lord is exemplified in Rama making friends with the hunter Guha and monkeys like Sugriv. Due to this quality, Krishna gave wealth to poor Sudama and changed an ugly-looking girl into a beautiful one.