How did John Stuart Mill use utilitarian arguments to defend freedom of speech?

John Stuart Mill defended freedom of speech using utilitarian arguments, positing that the unrestricted expression of opinion is essential for the progress and well-being of society.12

In his work On Liberty, Mill argued that legal or social restrictions on opinion are never justified because the "collision of adverse opinions" is a necessary component in the search for truth. He believed that without complete liberty of thought and discussion, civilizations risk becoming stagnant.23

Mill’s utilitarian framework emphasized that the value of a state is ultimately determined by the worth of the individuals who compose it. He contended that society requires the free play of speculative intelligence and the contributions of creative minds to avoid "ossification". Consequently, he maintained that the only legitimate reason for interfering with an individual's liberty—including their freedom of expression—is the prevention of harm to others, a principle known as the harm principle. By fostering an environment where ideas can be freely debated, society maximizes its potential for intellectual and social progress, thereby promoting the greatest happiness.321