To argue against "extreme view" of abortion – it is always impermissible, even to save the mother’s life (because there is a difference between killing (abortion) and letting die (abstaining)) – Thompson puts forth four statements on behalf of her opponents: (1) killing an innocent person is always impermissible, (2) killing an innocent person is murder and murder is impermissible, (3) not killing an innocent is more important that saving an already dying person from death, and (4) letting a person die is more acceptable than killing someone. Thomson counters these statements with two examples. The first, a variation of the violinist case, dictates that allowing the aforementioned violinist to use your body will eventually result in your death. The second explains a scenario of a rapidly growing baby sharing a tiny house with its mother. If the baby continues to grow, it will break the tiny house and walk out freely, resulting in the mother’s death; however, if the mother kills the child, she can walk out freely. Thomson argues that in both cases, the subject is allowed to act in self defence; to protect them self from harm even if it means killing an innocent, consequently disproving the premises of all four statements.
Thomson then furthers this argument to tackle the "weaker extreme view" – abortion is only permissible to save the mother’s life, but cannot be performed by a third party. She explains that because the mother is the owner of the house while the child is only a tenant, the mother has a right to life greater than the child’s. For example, if two men, Smith and Jones, were freezing and you, as a third party, are holding Smith’s coat, you are morally obligated to give it to Smith rather than to Jones.
To argue against the statement that killing the fetus is a violation of the basic right to life because everyone is entitled to the bare minimum needed to survive, Thomson puts forth the Henry Fonda example. If Thomson was on her deathbed and needed the touch of Henry Fonda to survive, she by no means entitled to this service. She has no positive right over Fonda to make him do this for her, just as the fetus has no positive right over the mother to support it in the womb. Alternatively, if we classify the right to life as the right not to be killed unjustly, we must prove that the fetus has been unjustly killed to say its right to life has been violated. Thomson uses another parity argument as an example. If you had a box of chocolates, it would be just to keep them for yourself, but unjust to give them to a child and then take it back. If a woman got pregnant without consent (rape) she can justly remove the fetus as she has given it no right to be there. However, if the woman had voluntary intercourse and full knowledge of the possible outcomes, she has to accept at least partial responsibility for her actions. The latter is further explained through the example of a house and a burglar. If you know that in your area, burglars climb through windows, and you leave your window open with as many preventative measures as possible – bars, netting, alarm systems – and the burglar still comes inside your house, you are responsible because you left the window open, but you still have the right to remove the burglar from your house. Following suit, if put forth all the precautionary measures you could, besides abstaining from sex (closing your window) and a fetus was still created, you have the right to remove it because you never invited it in.
Thomson ends on the topic of Good Samaritans and Minimally Decent Samaritans. She argues that if a Good Samaritan were to obtain a box of chocolates in front of a child, he would share it, although the Minimally Decent Samaritan wouldn’t. Humans are not morally or legally obligated to be Good Samaritans, rather, Minimally Decent Samaritans at best. So if a woman never gave the fetus an invitation to occupy the womb, she should not be morally or legally inclined to let it stay if it means more than minimal effort for the mother, as that is not the responsibility of a Minimally Decent Samaritan.