Freedom of expression has long been the subject of philosophical inquiry. Various theories have been furthered to explain and justify its protection, and, on top of this unsettled theoretical terrain, political debate is ongoing about how harmful expression should be addressed, including in the law.

In this context we should resist shifting focus from the freedom of expression to the harm of expression, and we should recall the liberal morality of freedom of expression in order to clarify how the liberal state may address harmful expression.

I will argue that freedom of expression is an absolute moral right, obligating the state not to interfere with expression on the basis of its appeal to independent reason. It is a precondition for liberalism, because it is necessarily entailed in the Kantian imperative of minimal inherent dignity and autonomy.

This deontological morality of freedom of expression has been neglected in consequentialist constructions of freedom of expression, which eschew the liberal presumption of capacity for independent reason, and focus upon harmful effects of expression.

I propose an Independent Reason Rationale for addressing harmful expression, to reorientate the state to its deontological obligations regarding freedom of expression. Limiting harmful expression inconsistently with that rationale breaches the moral right to freedom of expression.

The state might be forced to breach that right if it faces a conflict between it and another absolute moral right, like the right to life and security, but that breach remains a departure from liberalism.