cogency       
noun [ U ] uk/ˈkəʊ.dʒən.si/ us/ˈkoʊ.dʒən.si/
 (论据或理由)令人信服,有说服力,强有力
the fact of being clearly expressed and likely to persuade people
  I was struck by the cogency of his reasoning. 我被他推理的中肯所折服。 
 The message lacks cogency. 该信息缺乏说服力。 
 See: cogent
 - More examples
 - Even now the legislation lacks clarity and cogency.
 - The cogency of this distinction will be considered later.
 - The illegality of the action did not affect the cogency of the evidence.