Self-proclaimed “free thinker” Kanye West is now facing one of his biggest controversies yet. After making flippant remarks about America’s history with slavery, the rapper was hit with a wave of criticism from fans, friends, and experts on the subject. One such critic was Blair LM Kelley, a history professor at North Carolina State University.

First, let’s provide some background: during his recent appearance on TMZ Live, 'Ye regurgitated an unfortunately popular myth that slavery was a choice: “When you hear about slavery for 400 years … for 400 years? That sounds like a choice,” he said. “Like, you were there for 400 years and it's all of y'all? It's like we're mentally imprisoned.”

His ignorance of history was further demonstrated after he tweeted—and later deleted—a fake quote attributed to Harriet Tubman: “I freed a thousand slaves, I could have freed a thousand more if only they knew they were slaves.”

After receiving word about 'Ye’s comments, Kelley went to Twitter to provide a brief history lesson on American slavery, as well as the implications of the rapper’s words.

Kelley, an expert on African American studies, explained many people are unaware about the severity of slave treatment and how it’s too simplistic to suggest that all slaves could’ve easily escaped to freedom. You can read her full rebuttal in the tweets below.