Why we are able to recognize that human beings have intrinsic value is not of great importance to me in this paper. All that mattered was that one was able to recognize this value and then look at whom it should be extended to.
Your premise was that we recognize that all 'humans' have intrinsic value, and you said "most people agree that human beings have intrinsic value". Now this simply isn't true to say for all things that are genetically homo sapiens, as demonstrated by the abundant objection in this thread.
We might see an 'intrinsic value' in the disabled or infants, but from the simplest prokaryote upwards all life has some value of sorts, it's simply the case that value is relative.
If we take your explanation for intrinsic value then I feel it leads us to some very award conclusions. Namely, if we have intrinsic value because of our abilities and cognition then both new born babies and disabled persons will have less intrinsic value than other human persons. But surely this cannot be true.
I don't find these to be awkward conclusions. Just because disabled people and babies have less value than an adult human =/= they have no value whatsoever.
We can see immense value in an infant, because an infant has immense abilities, even if it's abilites and hence it's value are relatively less than an adult. I see no good reason the value must be considered exactly equal.
If we value an organism on it's demonstrated abilities, babies and disabled people have exponentially greater value than a foetus, which is worth less than a housemouse.
It is their being human that provides them with this intrinsic value - not their abilities.
I still can't grasp the rationale behind what is 'intrinsically valuable' about a particular nucleotide sequence, being valuable solely because it is a nucleotide sequence of a particular order.
