How does “slavery prove as injurious to his master’s wife”, as to Douglass himself? What does he mean when he says that “... education and slavery were incompatible with each other”?

While living at Master Hugh's for about seven years, Douglass learned to write. He did this despite not having a regular teacher, as his mistress had been forbidden to instruct him further. Douglass watched her transformation with a heavy heart. When he first came to her, she did not see him as chattel. She treated him like a human being and took care of his basic needs. Her cessation of instructing Douglass was her first step on the road to ruination. She went above and beyond her husband's request to leave off teaching her slave letters, and soon was most vigilant in making sure Douglass was nowhere near a newspaper. He was watched quite closely, but his own desire to read and write triumphed. Like her husband, she too would become full of rage, menace, capriciousness, and impatience. She was a perfect example of how slavery was not only detrimental for the slave but for the slaveholder as well.

Slavery and education were incompatible because when educated the slave understood his bondage and what he was missing out on...... that there was the possibility of another life...... a good life.

Literacy for Douglass is not only about liberating himself but also about integrating him into society and community - which were continually denied to him as a slave. Royer notes that when Auld explained why literacy was not appropriate for slaves, Douglass figured out that his master was not just talking about freedom but also his psychological wellbeing and his ability to take control of his own psyche. If Douglass was literate he would no longer be able to live in the system of slavery; he would be outside of it and try to run away with himself. Literacy "transforms the child-slave into a free-man."