1. Introduction . In the chapter which he devotes to the applications of his principle of individual liberty, Mill considers the question ‘how far liberty may legitimately be invaded for the prevention of crime, or of accident’. On the latter topic, he writes:—‘… it is a proper office of public authority to guard against accidents. If either a public officer or anyone else saw a person attempting to cross a bridge which had been ascertained to be unsafe, and there were (...) no time to warn him of his danger, they might seize him and turn him back, 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.”. (shrink)