Question

Why do slaves need to be kept ignorant

Answer 1

if slaves are kept ignorant, they would have limited knowledge, and doing this would also keep a boundary, people at the time believed that white people should be educated since they were "superior" and slaves had no need to be educated since they were basically livestock in their eyes.

Answer 2

Before, Slave owners kept slaves treated like dirt/animals. That was thier job. Sadly, Slaves were restricted to not be educated, or learn anything. All the slaves knew to do was listen to thier masters and work work work.