You can rephrase the question in the title as follows: “what do human rights have in common?”, or “what is the essence of the idea of human rights?” Michael J. Perry offers a general formulation in The Idea of Human Rights:
[T]here is something about each and every human being, simply as a human being, such that certain choices should be made and certain other choices rejected; in particular, certain things ought not to be done to any human being and certain other things ought to be done for every human being.
I like this formulation because it brings out several key aspects of human rights:
- The fact that human rights can be negative or positive: they may demand that we refrain from doing certain things (torture, kill etc.), and they may demand that we do certain things (help, protect etc.). In fact, most human rights are both negative and positive at the same time.
- There is indeed “something about human beings” that make human rights necessary and that make them human rights, i.e. rights that belong only to human beings. Human beings value certain things, things that aren’t valued – or are less valued – by other creatures: thinking, identity, belonging, peace, prosperity, freedom and equality. And they need human rights to realize these values. Animals don’t need free speech, not only because they can’t speak (the ability to speak isn’t a sufficient condition to have a right to speak) but also because they don’t need free speech to search for the truth. This doesn’t mean that animals can’t have animal rights, or that certain human rights can’t also be animal rights (for example those rights that protect the value of non-pain, a value that humans share with animals – animals can be tortured just like humans, although probably not always for the same reasons).
More posts in this series are here.