From an online debate: how do you recognize a natural right?
...There are two ways to be certain of the difference between a true and false right, a right in natural law and a right designed by some political entity to suit itself. The first is that the obverse of a right is a duty. A right is always a claim made on the rest of mankind. The obverse of the right to life is the duty not to lay violent hands on another man, however infuriating the person. (I am speaking of adults here, setting the issue of abortion aside.) The right to liberty is the obverse of the duty not to interfere with anyone except for specific and legal reason. The right to the pursuit of happiness is the obverse of the duty not to muck about in any way with the soul of another person for your own ideology or convenience. I have seen this right brutally violated in the case of a man who had fallen in with a particularly poisonous sect. The right to property is the obverse of the duty not to steal; the right to privacy, of the duty not to break into someone's private house and life without very good reason. As the wise old joke has it, the freedom of my fist's motion is limited by the position of my neighbour's nose. And when you try to define what is obverse of this supposed right to abortion, you have a problem. What is its obverse? Who owes you a duty in this respect? The doctor? Setting aside such matters the Hippocratic oath and the Ronald Thatcherite idea of the doctor as a provider of services to be paid in cash, the fact is that a doctor is not a necessary part of an abortion at all. I am not even thinking of unqualified practitioners and faiseuses d'anges; it is perfectly possible, if risky, to abort one's own child alone. The only two necessary terms to an abortion are the mother and the child; and it follows that if such a thing as a right to abortion exists, its obverse is the child's duty to die. At which point some of us can begin to see a problem.
The other way to identify a genuine right is that it will always have universally recognized exceptions. The right to life is abridged by such things as war, legitimate police activity, and individual self-defence. The right to liberty can be abridged by conscription or by conviction in a court of law. The right to pursuit of happiness, of course, falls aside in such cases, and is also curtailed if the "happiness" in question were that of a sadist or of a bandit. The right to property is limited by taxation and by any form of lawful confiscation; the right to privacy, by the public interest in investigating wrongdoing and defending persons at risk (an abusive parent loses the right to privacy, along with his/her parental rights, the moment the privacy of his/her house becomes an instrument of torment). But no such limitation can be identified in the "right" to abortion.
The other way to identify a genuine right is that it will always have universally recognized exceptions. The right to life is abridged by such things as war, legitimate police activity, and individual self-defence. The right to liberty can be abridged by conscription or by conviction in a court of law. The right to pursuit of happiness, of course, falls aside in such cases, and is also curtailed if the "happiness" in question were that of a sadist or of a bandit. The right to property is limited by taxation and by any form of lawful confiscation; the right to privacy, by the public interest in investigating wrongdoing and defending persons at risk (an abusive parent loses the right to privacy, along with his/her parental rights, the moment the privacy of his/her house becomes an instrument of torment). But no such limitation can be identified in the "right" to abortion.