Here is Udo's latest take on the nebulous concept of "human dignity" - a concept that I consider to be essentially a myth, at best a false rationalisation of other, more specific and genuine values.
Udo is seeking feedback, so feel free to give him some. As far as I'm concerned, he is on the right track. There is no special moral "dignity" or "worth" that goes with being human, i.e. the species Homo sapiens (as opposed to having such characteristics as sentience, personhood, vulnerability to disappointment and psychological suffering, and so on). That's not to deny the possibility of some acceptable degree of speciesism: if, for example, we just do value the continuation of our species, not as a means to some other end but as an end in itself, then it is rational for us to develop social norms that might achieve this. Thus, in a Battlestar Galactica situation, where our species is almost extinct after a terrible attack by powerful and malevolent Cylons, strongly pro-natalist social norms might be rationally justified in a way that they are not in actual societies where the rational imperative is more to retard population growth.
Surely, though, the preservation of Homo sapiens is not all that we value, or even a very important source of our morality. For example, we value the amelioration of suffering for all sentient living things, regardless of species - don't we?
Indeed, imagine that there are other species of intelligent lifeforms with which we are capable of social interaction, and that we and they have collaborated to establish thriving multi-species societies. If some loyalties (e.g. to a philosophical tradition, or an artistic practice) crossed the species boundaries, why would anyone necessarily think the preservation of one or another species more important than the preservation of something else that she is loyal to? In that context, what would be so great about the preservation of something that happens to have a certain sort of DNA? Mightn't it be more important to preserve the tradition of Vogon poetry? Okay, bad example - but you get the idea.
The concept of human dignity has some useful work to do if it is (no more than) a sort of code for the idea that human beings of all so-called "races" (a very dubious biological concept) are really very similar, and have very similar moral claims to our kindness and consideration. Yes, "human dignity" is a good, because familiar, phrase to signal our repudiation of Nazism and all kinds of racism. But once attempts are made to use it as a more precise moral concept, within an ethical system, it becomes a false rationalisation of our morality. It can then lead to absurd results, such as the idea that the destruction of a human embryo, or even a zygote, is of similar moral significance to the murder of a fully-formed human child or adult who has hopes, fears, physical and psychological sensitivities, and everything else that goes with personhood. Used as it is by conservative moralists of various kinds, "human dignity" is a concept that we'd be better off without; the sooner that particular meme is expunged from our systems of formal ethics, the happier I'll be.