As for the aliens with hearts, of course that is possible. In fact, if you want an example of persons with hearts you don’t need to imagine it: you and I are good examples. The point of the alien thought experiment is that it is conceivable that there could be persons of some kind without hearts. But again, we don’t have to imagine examples of this phenomena: there are now in reality people with artificial blood-pumping mechanisms instead of hearts. These examples seem to me like very good reason to consider a beating heart incidental to being a person.

Your last point is extremely confusing. Do mollusks and insects have consciousness? I have no idea, but I am willing to bet that they do in some extremely primitive form. Does that make them persons? Not necessarily.

Is that supposed to be a problem for me? I don’t see how it is. I never claimed that consciounsess in any form whatsoever is sufficient for personhood. That would definitely be a crazy view. I merely said that consciousness seems like an obvious, necessary condition for being a person. Point being: that rules out fetuses (at early stages of development).

In medicine, a coma (from the Greek koma, meaning deep sleep) is a profound state of unconsciousness. A comatose patient cannot be awakened, fails to respond normally to pain or light, does not have sleep-wake cycles, and does not take voluntary actions. (Wikipedia

As far as your aliens theory goes, what if their biology was such they they didn’t have brains or a spinal column but instead their intelligence came from a beating heart? It’s essentially the same argument.

The same thing with the mollusks and insects. Would you say they have no consciousness? Just because animals have brains doesn’t make them persons either.

So in essence I don’t your arguements would persuade my beliefs either way.

As far as the beating heart, I don’t really see how that would be important. This is where things get a bit more philosophical. Consciousness is clearly central to our conception of a normal, healthy adult person. When we talk about persons as the locus of moral consideration, it is largely due to their consciousness that we are concerned with their interests. So to generalize this idea, consciousness is one of the most important criteria to look for in any organism when we are concerned with whether it is a person. On the other hand, a beating heart seems totaly accidental and unimportant to personhood.

For one thing, we now have artificial hearts available. Someone who has one of these plastic mechanisms in their chest is still every bit a person, they just happen to lack a heart. Alternately, suppose aliens landed on Earth who were very much like us in terms of their level of consciousness, their ability to comunicate through complex language and thought, their ability to reason, makes plans, and choose which activites to pursue, but their biology is such that they don’t have hearts. We would still consider them persons.

Now think about all the creatures like mollusks and insects that have hearts, but don’t even approximate to being persons. What all these examples are meant to demonstrate is that “having a beating heart” is totally accidental to personhood. Having a beating heart is neither a necessary nor sufficient condition for something to be a person, it is just not essential to our status as the locus of moral consideration.

But hey, talk about defeasible theories! If you thought science was bad, philosophy is even worse. The best argument I can offer for my conclusion, the type of argument above, makes explicit appeal to moral intuition. And insofar as our intuitions diverge, we do face a problem reaching consensus in moral debate. Still, one hopes that more often than not intuitions will match and lead us to the same results. I would definitely be interested to hear what you think about anything I’ve said.

The embryonic heart starts beating 22 days after conception, or about five weeks after the last menstrual period, which by convention we call the fifth week of pregnancy. The heart at this stage is too small to hear, even with amplification, but it can sometimes be seen as a flickering in the chest if an ultrasound is done as early as four weeks after conception.

Would you consider this important data as well?

Colin: “It seems to me that there are other ways, like by appeal to general, widely agreed upon, but secular principles of right action.”

I guess that is where my religious beliefs also lead me to make no real distinction between “secular principles of right action” and “appeal to religious authority” because I feel that our feelings of what is write and wrong come from the Spirit of Christ as stated in Moroni 7:16-17. I think this is in essence what you would term as “moral intuition”:

For behold, the Spirit of Christ is given to every man, that he may know good from evil; wherefore, I show unto you the way to judge; for every thing which inviteth to do good, and to persuade to believe in Christ, is sent forth by the power and gift of Christ; wherefore ye may know with a perfect knowledge it is of God.

But whatsoever thing persuadeth men to do evil, and believe not in Christ, and deny him, and serve not God, then ye may know with a perfect knowledge it is of the devil; for after this manner doth the devil work, for he persuadeth no man to do good, no, not one; neither do his angels; neither do they who subject themselves unto him.

Your right, science may not be completely useless, but also I don’t think a “well-worked-out theory of human psychology” would be any more useful in a debate. Look at the debates going on about psychology right now (i.e. Tom Cruise ;))

I think a more appropriate scientific approach would be to observe when the heart starts beating and there is brain activity in a fetus. These two things seem to play a major role as to when we determine the death of a person, so why not use this data to determine the life of a person? I don’t know the exact data but I was in an infertility clinic a couple weeks ago and looked through a book that detailed the whole life cycle of a fetus. It seemed to suggest that both of the aforementioned events occurred within the first trimester.