Answer:
By 'isness' of humanity's present nature, King meant moral incapibility of humankind to do what is morally obligatory or morally right.
Explanation:
Martin Luther King was bestowed with the Nobel Prize on 11th December, 1964. King was the leader of the Civil Rights Movements, although the movement was sundry to bestow one person the Nobel Prize.
In his speech, he began with reflecting great grief on the loss of lives during this movement. He said
'I refuse to accept the idea that the “isness” of man's present nature makes him morally incapable of reaching up for the eternal “oughtness” that forever confronts him.'
The term 'isness' refers to the state of being or existence. By 'isness' of humanity's present nature, King meant to say that he refuse to accept that humankind is morally incapable of doing what is morally right or obligatory. The 'existence' of man's present nature of inability to do what is morally right is unacceptable in the eyes of King.
