Former Defense Secretary Jim Mattis, during a panel discussion, said he believed that the country’s education system needed to reemphasize certain principles, including teaching “the good, the bad, the ugly.”

During his live-streamed talk with the Office of Strategic Services Society on Thursday, Mattis said he believed that education in the U.S. should not gloss over uncomfortable topics, such as the effects of slavery, which still reverberate in contemporary society.

“As I look at the way American history is taught in our public schools, in many of our universities, I’m not sure how much affection I would be building in my students the way it’s being taught,” Mattis said.

“I believe in teaching the good, the bad, the ugly — and our country was born with a birth defect that we imported from the Old World — called slavery — and we’re still dealing with the after-effects of it,” he added.

Mattis’s comments come as senior U.S. military leaders have grappled with the racial inequality protests throughout the country in recent months. The protests culminated in a dramatic stand-off as National Guard forces were deployed in several states and federal troops were placed on stand-by orders in the summer.

Military leaders like U.S. Army Gen. Mark Milley, chairman of the Joint Chiefs of Staff, issued memos saying that the services were aware of the “frustration” many Americans were feeling and that the military needed a transparent discussion about the effects of racial injustice.

Admiral Mike Gilday, the Navy’s top officer, said in a video that, “we can’t be under any illusions about the fact that racism is alive and well in our country… and I can’t be under any illusions that we don’t have it in our Navy.”

U.S. Air Force Chief of Staff Gen. Charles “CQ” Brown Jr., who is African-American, also released an emotional video outlining his own experience in the workplace.

The generals’ consensus comes as some congressional lawmakers have repeatedly downplayed the effects of racial injustice in recent years. Republican Rep. Scott Perry of Pennsylvania previously questioned whether racial injustice is a widespread problem in the country, saying that “if there’s a system, someone had to create that system.”

“Someone is operating and nurturing the system to keep it going,” Perry said in 2020, according to The York Dispatch. “I don’t know who in our country is doing that… That belies the fact we had a war among the United States over that issue to cleanse our country of that issue.”

Jim Mattis, who earned a reputation as “warrior-monk” for his scholarship while in uniform, noted that the country’s “first principles” ought to be reinforced in the classrooms.

“How many of us are brought up today with a love for America?” Mattis said. “How many of us realize that we have no ordained right to exist — that every generation has had to fight for this freedom, this, what George Washington in his first inaugural called ‘an experiment?'”

“There’s just a sense that ‘we’ve just got it,'” he added. “And we’ve got to get back to that and understand how precious this is.”

This article was written by David Choi and originally published on Business Insider.