The pro-life argument from substantial identity and the pro-choice argument from asymmetric value: a reply to Patrick...

Lee claims that foetuses and adult humans are phases of the same identical substance, and thus have the same moral status because: first, foetuses and adults are the same physical organism, and second, the development from foetus to adult is quantitative and thus not a change of substance. Versus the first argument, I contend that the fact that foetuses and adults are the same physical organism implies only that they are the same thing but not the same substance, much as living adults and their corpses are the same thing (same body) but not the same substance. Against Lee's second argument, I contend that Lee confuses the nature of a process with the nature of its result. A process of quantitative change can produce a change in substance. Lee also fails to show that foetuses are rational and thus have all the essential properties of adults, as required for them to be the same substance. Against the pro-choice argument from asymmetric value (that only the fact that a human has become conscious of its life and begun to count on its continuing can explain human life's asymmetric moral value, i.e. that it is vastly worse to kill a human than not to produce one), Lee claims that foetus's lives are asymmetrically valuable to them before consciousness. This leads to counterintuitive outcomes, and it confuses the goodness of life (a symmetric value that cannot account for why it is worse to kill a human than not produce one) with asymmetric value.