Having reviewed the above arguments and counter-arguments, Don Marquis goes on (in "Why Abortion is Immoral", 1989) to offer a sharper and more comprehensive criterion: terminating a life is morally wrong because a person has a future filled with value and meaning, similar to ours. But the whole debate is unnecessary. There is no conflict between the rights of the mother and those of her fetus because there is never a conflict between parties to an agreement. By signing an agreement, the mother gave up some of her rights and limited the others. This is normal practice in contracts: they represent compromises, the optimization (and not the maximization) of the parties' rights and wishes. The rights of the fetus are an inseparable part of the contract which the mother signed voluntarily and reasonably. They are derived from the mother's behaviour. Getting willingly pregnant (or assuming the risk of getting pregnant by not using contraceptives reasonably) - is the behaviour which validates and ratifies a contract between her and the fetus. Many contracts are by behaviour, rather than by a signed piece of paper. Numerous contracts are verbal or behavioural. These contracts, though implicit, are as binding as any of their written, more explicit, brethren. Legally (and morally) the situation is crystal clear: the mother signed some of her rights away in this contract. Even if she regrets it - she cannot claim her rights back by annulling the contract unilaterally. No contract can be annulled this way - the consent of both parties is required. Many times we realize that we have entered a bad contract, but there is nothing much that we can do about it. These are the rules of the game. Thus the two remaining questions: (a) can this specific contract (pregnancy) be annulled and, if so (b) in which circumstances - can be easily settled using modern contract law. Yes, a contract can be annulled and voided if signed under duress, involuntarily, by incompetent persons (e.g., the insane), or if one of the parties made a reasonable and full scale attempt to prevent its signature, thus expressing its clear will not to sign the contract. It is also terminated or voided if it would be unreasonable to expect one of the parties to see it through. Rape, contraception failure, life threatening situations are all such cases.