COMMENT | Last month, the Journal of Controversial Ideas – of which I am a co-editor – published its first issue. The journal is a response to the shrinking boundary, even in liberal democracies, of acceptable discourse.

It is specifically designed to provide a forum in which authors can, if they wish, use a pseudonym to avoid running the risk of receiving personal abuse, including death threats, or of irrevocably harming their careers.

There was a time when the threat to academic freedom in democratic countries came primarily from the right. The free speech cause célèbre of the early twentieth-century United States featured Scott Nearing, a left-leaning economist at the University of Pennsylvania who was dismissed because his activism for social justice did not sit well with the bankers and corporate leaders on the university’s board of trustees.

Fifty years later, in the McCarthy era, many people were blacklisted or dismissed because of their support for leftist ideas. When I came to Princeton in 1999, Steve Forbes (who was then campaigning for the Republican nomination for president) called for my appointment to be rescinded because he objected to my critique of the traditional doctrine of the sanctity of human life.

Today, however, most of the opposition to freedom of thought and discussion comes from the left. One exemplary instance occurred in 2017 when Rebecca Tuvel published 'In Defense of Transracialism' in Hypatia, a journal of feminist philosophy.

Tuvel’s article asked why people who strongly support the right to choose one’s gender deny a similar right to choose one’s race. Over 800 people, mostly academics, signed a letter demanding that ...