The harm principle and freedom of belief

What does the harm principle mean when it comes to questions around freedom of religion and belief?

Mill wrote that ‘If [anyone] saw a person attempting to cross a bridge, which had been ascertained to be unsafe, and there was no time to warn him of the danger, they might seize him and turn him back around without any real infringement of his liberty, for liberty consists in doing what one desires, and he does not desire to fall into the river’.

St Augustine used a very similar argument about protecting somebody from a collapsing building to argue the case for the persecution of heretics and restrictions on the freedom of belief. Forcing a person to change their heretical beliefs by any means necessary would be a form of mercy. It would save them from the harm of eternal punishment. If an absence of religious belief will lead to harm in the next life, then should the state not have the right – or even the duty – to remove religious freedoms? Why would it be OK to pull somebody back from the falling bridge or building, but not OK to interfere with their ‘dangerous’ beliefs?

One might argue that we have better evidence about what will happen in the bridge case, but this is unlikely to persuade the convinced believer.

In response to this dilemma the philosopher Alan Haworth says ‘[Today] religion has become, in a sense, irreversibly privatized: no one else’s business and certainly not the state’s’.

It might be acceptable for other believers to try to persuade you to change your beliefs (indeed, one might wonder why more do not try). However, it is not the role of the state to interfere.