The luckies are a species of intelligent beings, very much like humans intellectually, a species that has produced a culture of about the same level as we have. Luckies reproduce sexually, and their intellectual development proceeds at the same pace as that of humans. Thus, they begin their organic existence as a unicellular organism, and then grow quickly. Initially, they have no intellectual life to speak of. After a couple of weeks, just as a human embryo, a lucky develops a brain, and eventually becomes conscious. At nine months from fertilization, a lucky is quite helpless, just as a newborn human infant is. Up to around 21 months from fertilization, a lucky is just starting to catching up to the intelligence of an average dog, just as humans do at around 12 months after birth. At around 27 months from fertilization, luckies begin to recognize themselves in mirrors, and around five years after fertilization they become capable of uttering sentences involving embedded conditionals.[note 1]
But there is a crucial difference between the luckies and us. The luckies are fortunate enough to live in a natural environment empty of predators that could eat a small lucky, on a planet covered with vegetation whose nutrition a lucky for the first nine months from conception can absorb through the skin, and after that the lucky can easily suck the nutrition out of the vegetation. The fertilization of luckies, thus, happens externally to the body of both parents, and the resultant unicellular lucky, which will double in bulk every twelve hours for the first couple of days, is simply left on the vegetation in the parents' garden, to grow. Eventually, at about 8-10 months after fertilization, the parents start playing with the lucky, because although the lucky doesn't have any physical needs that call upon the parents, nonetheless its emotional and intellectual development from that point on starts to require interaction with other luckies.
My argument now has three stages:
- Killing human infants is murder.
- Therefore, killing luckies at any stage of their development is murder.
- Therefore, killing humans at any stage of their development is murder.
Stage 1: I shall simply take it for granted that killing human infants is murder. There is no real controversy about this, except in the case of some philosophers who don't know when they have a reductio ad absurdum on their hands. In fact, we tend to think that there is something particularly barbaric about killing infants, and we do not think there is anything irrational in a parent sacrificing his or her life to save an infant, in a way in which it would be irrational to sacrifice one's life for one's dog.
Stage 2: Plainly, if to kill a human infant is murder, it is equally murder to kill a lucky from about nine months from fertilization on. For the lucky nine months after fertilization has the same kinds of actual and potential agentive and intellectual abilities that the human infant does. The difficulty is whether we can push this judgment back to the time of a lucky's fertilization.
Suppose we deny this. Then, while it is murder to kill a lucky at the nine month point, it is not murder to kill a lucky at the beginning. At some point a transition occurred, a transition from a lucky not being the kind of thing that has a right not to be killed (or, maybe, a right not to be killed unless one has done something to deserve it—the details here won't affect the argument much, I think), to a lucky being that sort of thing. What makes for that transition? Remember that in the developmental history of a lucky, there is no such thing as birth—luckies live autonomously from fertilization.
I see two possible transition points other than fertilization. The first is the coming into existence of the lucky's brain (or whatever the equivalent in a lucky is), and the second is the beginning of consciousness. I think neither transition point is plausible, for the following reasons. First, the mere existence of a brain that isn't actually thinking consciously gets you little of moral significance, unless one thinks that the brain is the individual or something like that, so that the individual comes into existence when the brain does. This is implausible. It is not my brain that is the thinker. It is I who think, at least in part, with my brain. Moreover, once one admits that a barely existent brain of a lucky is sufficient to ground a right not to be killed, I think one has admitted that things gain moral significance from what they naturally develop into it. For initially the brain of a lucky is, presumably, a poor affair (I assume it is like the brain of a human embryo), of less actual computational ability than the brain of an adult chicken, and I take it that adult chickens do not have a right not to be killed. What makes the brain of the lucky at all significant is that it has a natural propensity to develop into a brain capable of the kinds of intellectual skills that are distinctive of luckies and humans. But once such natural propensities are seen as sufficient to confer a right to life, then we have to say that a lucky has a right to life at fertilization, since the lucky at fertilization already has such a natural propensity. Consciousness is no more helpful as a transition point. It seems plausible that all mammals have consciousness, but not all mammals have a right not to be killed. By itself consciousness cannot have the relevant kind of significance, unless perhaps one takes a Cartesian view on which we are essentially conscious, so that consciousness is a necessary condition of our existence. But then we have to say, with Descartes, that all appearances to the contrary notwithstanding, no matter how deeply we are asleep, we are conscious—else we cease to exist. This is implausible.
So we cannot mark a transition point in the life of a lucky between fertilization and nine months where a lucky would gain a right to life. Thus, we need to suppose that the lucky has always had that right, perhaps in virtue of its natural propensity to develop into an intelligent adult lucky.
Step 3: Observe that luckies and humans for the first nine months after fertilization do not seem very different intrinsically. The only difference is that the luckies find themselves in a natural environment that is much more friendly than the natural environment on earth. Thus, humans can currently only survive for that part of their development in a controlled environment in utero, luckies have that kind of an environment out in their parents' garden. Granted, the human embryo is more dependent on the mother than the lucky at the same stage of development. But the lucky is no less dependent—it's just that the dependence is not on the mother, but on the vegetation, the air, and other aspects of the environment. That, however, should not make for a difference in the lucky's moral status, just as, if we engineered an environment (e.g., an artificial womb) where humans could develop for the first nine months from fertilization, a human in this environment would not have any different moral status from a human in a womb.
If we had any reason to think an embryonic or fetal human was a mere part of the mother on whom it depended, maybe we could try to build an argument for the permisibility of killing it on that basis. But, first of all, embryonic and fetal humans are not a part of the mother, since their development has different goals from the mother's—they do not subserve the mother in the way a part does.