Teaching slaves to read was illegal because it was believed to be a threat to the institution of slavery. Slave owners feared that if slaves were able to read, they might become educated about their rights and become less likely to submit to their masters. Literacy and education also allowed slaves to read abolitionist literature which motivated and inspired others. Furthermore, education allowed slaves to share information with each other and gain a sense of autonomy and control over their lives, which could potentially lead to rebellion or escape.