{We know that this is our son, and that he was born blind}
(Oidamen hoti houtos estin ho huios h(886d)(936e) kai hoti tuphlos
egenn(8874)h(885c)). These two questions the parents answer clearly and
thus cut the ground from under the disbelief of these Pharisees
as to the fact of the cure (verse  18 ). So these Pharisees made
a failure here.