What is political extremism? Professor of psychology Jordan Peterson points out that America knows what right-wing radicalism looks like: The doctrine of racial superiority is where conservatives have drawn the line. "What’s interesting is that on the conservative side of the spectrum we’ve figured out how to box-in the radicals and say, 'No, you’re outside the domain of acceptable opinion,'" says Peterson. But where's that line for the Left? There is no universal marker of what extreme liberalism looks like, which is devastating to the ideology itself but also to political discourse as a whole. Fortunately, Peterson is happy to suggest such a marker: "The doctrine of equality of outcome. It seems to me that that’s where people who are thoughtful on the Left should draw the line, and say no. Equality of opportunity? [That's] not only fair enough, but laudable. But equality of outcome…? It’s like: 'No, you’ve crossed the line. We’re not going there with you.'" Peterson argues that it's the ethical responsibility of left-leaning people to identify liberal extremism and distinguish themselves from it the same way conservatives distance themselves from the doctrine of racial superiority. Failing to recognize such extremism may be liberalism's fatal flaw.