The Third Variation picks up where the Second leaves off:
| Step 1: | 1 | Every fetus is a person. | |
| 2 | Every person has a right to life. | ||
| Therefore | 3 | Every fetus has a right to life. | 1&2 |
| Step 2: | 4 | No being with a right to life may be killed unless it is a fetus whose development threatens the pregnant woman's life. | |
| Therefore | 5 | No fetus may be killed unless its development threatens the pregnant woman's life. | 3&4 |
What does it mean to say that someone has a right to life?
| A1: | If x has a right to life then x has a right to at least the bare minimum necessary for x's continued survival. | ||
| Thomson's response: | Suppose all she requires for continued survival is the cool touch of Henry Fonda's hand on her fevered brow. Does he have an obligation to fly to the east coast and touch her fevered brow? No. Thus A1 is false. | ||
| A2: | x has a right to life iff x has a right not to be killed. | ||
| Thomson's response: | But we have already agreed that one does not bear an obligation to the violinist to remain hooked up. ThusA2 is false as well. | ||
Hence,
| 1 | If A1 and A2 are false, then if x has a right to life then x does not have the right to the use of another person's body and x does not have the right to the continued use of another person's body. | ||
| 2 | A1 and A2 are false. | ||
| Therefore | 3 | If x has a right to life, then x does not have the right to the use of another person's body and x does not have the right to the continued use of another person's body. | 1&2 |
| 4 | If (3) then it is false that no fetus may be killed unless its development threatens the pregnant woman's life. | ||
| Therefore | 5 | It is false that no fetus may be killed unless its development threatens the pregnant woman's life. | 3&4 |
But then it follows that premise 4 of Variation Three is false.