What is Cornel West arguing when he argues for “prophetic thought?"

As per West's inclusion of Whitman's idea from 1871, prophetic thought suggests that there is always an unrecognized vista of human expression and social identity for which struggle is always present.  Whitman's assertion of Prophetic Thought argues that there can be no finality to the struggle for human rights and individual expression.  This flies in the face of American Exceptionalism in its assertion that there will always be a struggle which needs to be articulated:

The cloud breaks a little and the sun shines out but soon and certain the lowering darkness falls again as if to last forever.  Yet is there an immortal courage in every sane soul that cannot, must not, under any circumstances capitulate.  Viva the attack!  The perennial assault.  Viva the unpopular cause, the spirit that audaciously aims, the never abandoned effort pursued the same amid opposing proofs and precedents.

This is where the term arises.  At the same time, West's inclusion takes this to a modern setting, arguing that while progresses have been made to many silenced voices in bringing them to the surface, individuals cannot be complacent in this struggle, and cannot capitulate to globalized comfort in pretending that this is not a reality.  The postmodern condition of which West speaks demands that individuals still arm themselves with a sense of "prophetic thought," in terms of how reality is viewed.  Regardless of the fact that democracy seems to have emerged from the Cold War as "the winner" and that advancements in globalization have spread the doctrine of liberal individualism to more people, prophetic thought mandates that we, as individuals, construct consciousness with a sense of prophetic thought, demanding that we still are attune to others' suffering, to the "unpopular cause" and uphold "the attack."