“unable” = the reason the Jews don’t understand what Jesus is teaching is that they are incapable of hearing His word. It is not that they are intellectually unable to understand; their problem is spiritual deafness. They cannot perceive the truth of what Jesus has said because their own preconceptions have kept them from it. Jesus does not tell them the things they expect to hear and, thus, they cannot spiritually understand. But, in the final analysis, the problem is not that they have no ability to hear or to understand; the problem is that they refuse to hear what He is saying. “A man will only hear what he wishes to hear.” (Barclay) Those who “can not” hear the words of Christ most often “can not” because they “will not.” An example is found in the Jews response to the words of Stephen in (Acts 7:57).

Acts 7:57  At this they covered their ears and, yelling at the top of their voices, they all rushed at him,