Conversation so far:
What did the philosopher Madvacharya believe?
Madhva studied the Upanishads and the Advaita literature, but had frequent disagreements with his guru.
Why did Madhvacharya oppose his guru?
Madhva was unconvinced by its nondualism philosophy of oneness of human soul and god.
Did Madhvacharya have any issues with other gurus, besides his first teacher?
Madhvacharya was a fierce critic of competing Vedanta schools.

Question: Who did Madvacharya agree with?
Self-contained rewrite: Who did the philosopher Madvacharya agree with?