Thomson's Variation

Noonan's Argument:

1

If x is an act of harming a human being and x has no sufficient reason, then x is morally wrong.

2

If x is an abortion then x is an act of harming a human conceptus (embryo, fetus).

3

A human conceptus is a human being.

Therefore

4

If x is an abortion then x is an act of harming a human being.

2&3

5

If x is an abortion then, if x is not a case of cancerous uterous or ectopic pregnancy, then x has no sufficient reason.

Therefore

6

If x is an abortion and x is not a case of cancerous uterous or ectopic pregnancy, then x is an act of harming a human being and x has no sufficient reason.

4&5

Therefore

7

If x is an abortion and x is not a case of cancerous uterous or ectopic pregnancy, then x is morally wrong.

1&6

Thomson's Variation:

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

A fetus' right to life is more stringent than a mother's right to determine what happens in and to her body.

5

If a fetus' right to life is more stringent than a mother's right to determine what happens in and to her body, then no fetus may be killed.

Therefore

6

No fetus may be killed

4&5

1

Noonan's Argument is valid, as is Thomson's Variation.

2

Both arguments take two steps.

3

Both arguments assume that the human conceptus is a human being.

• Premise (3) in Noonan's Argument

• Premise (1) in Thomson's Variation

4

Premise (4) in Thomson's Variation is an analog of Premise (5) in Noonan's Argument.