Q.One man's rights end where the other man's nose begins.

The saying captures the core idea of this chapter's discussion of responsibilities: no one's rights are unlimited, because they run up against the equal rights of everyone else. …

On one reading, the saying is exactly what this chapter's second responsibility describes: rights require us to respect the same rights in others, so my freedom is limited by the principle that everyone is entitled to equal and identical rights. If I do not want others interfering in choices I make for myself, I must equally refrain from interfering in theirs; I cannot use my own right to free expression to incite violence against my neighbour, because doing so would violate my neighbour's more basic right to safety. In this sense, the 'nose' in the saying stands for another person's own body, dignity, and rights, echoing Kant's argument that we must never treat another person merely as a means to our own ends — my freedom cannot be exercised in a way that turns someone else into a mere target or obstacle.

The saying also captures the chapter's third responsibility, balancing conflicting rights. My right to freedom of expression lets me take photographs, but if I use that right to photograph someone inside their own house without consent and publish the images, I have crossed into violating their right to privacy — precisely the tension the chapter illustrates with the example of a sting operation that infringes a person's privacy even while claiming to serve public interest. …