Question

robust knowledge requires both consensus and disagreement

Answer 1

Agreement and disagreement, both are required to make knowledge robust. Knowledge has to be supported by the people. It does need consensus to be strong. 

But knowledge can prove its mettle only when there is contradiction. The strength of knowledge can be seen when it is able to survive criticism. Knowledge which has passed the test of disagreement is considered to be strong. 

So both consensus and disagreement are needed to build robust knowledge.