One time Bhattar asked Ramanuja: "Could we not use another pramANa, other than Dvaya mantra, to understand the meanings expressed by it?"

Ramanuja replied: "If there is another pramANa that brings out the full meanings shown by Dvaya, it can be used. However, there is no such thing. That is why, Azhvars and Acharyas used Dvayam itself to express these meanings".