But a wise historian is precisely what the Rev. Robert Strickland is not.
请教老师：此处的what如何理解？这里是复合关系代词指代人吗？麻烦老师讲解剖析一下此处的what如何理解？
你一定在答疑网看过有关关系代词指人在限制性定语从句中作归属性表语时，只可以用that（或省略that）不可以用who的问题和解答。其原理是，归属性表语表示一个人的身份、职业、素养等，而不是这个人本身，所以用that引导从句而不可以用who。
同样的道理，what引导名词性关系分句时，只须what在分句中作归属性表语，就能指人的职业、身份、素养等。
But a wise historian is precisely what the Rev. Robert Strickland is not.
= But a wise historian is precisely the kind ofperson thatthe Rev. Robert Strickland is not.
你可以了解的看出，what替换成the kind of person that, that在限制性定语从句中作归属性表语。这就是为何what可以指人的道理所在。