CNN's Anderson Cooper asked Comey what gives him the belief that institutions like the FBI are strong enough to handle the criticism they face from the White House.
"Because I know them," Comey said. "And because I know no president serves long enough to destroy the culture at the root of them."
Of the term "deep state" that Trump supporters so frequently throw around when speaking of Trump critics in US government, he said, "There is no deep state but there is a deep culture. The fundamental values that are at our constitution that runs deep. The FBI, the justice department as a whole. The intelligence community. It is the ballast that gives me comfort and I hope gives all Americans comfort."
"If we are silent," he added, "tremendous damage will be done that will take us time to recover."