How does dehumanization render a person powerless? How were slaves dehumanized?

One of the most important ways slaves were kept in bondage was not simply the threat of physical brutality; rather, it was through deep and sustained ignorance and dehumanization. Slaves were not allowed to read and write and were thus generally not aware of the events outside of the plantation, could not communicate with each other well to foment rebellion or conduct escape plans, and could not attain the sense of self-sufficiency and pride that came from being lettered. Literacy brought with it an understanding of the larger world. It opened up before a slave the idea of justice and an understanding of history. Making slaves feel less than human made them resigned to their fate and easier to control.