What makes humans valuable? There are only two options: something inherent within the nature of humans themselves (intrinsic) or something acquired by humans (extrinsic). Things that are valuable in and of themselves for the sake of themselves have intrinsic value (love, friendship, health, happiness, virtue, etc.). Things that are valued for their function – what they do for us or how they allow us to obtain an intrinsic good (money) – have extrinsic value.
When it comes to bioethics, the great divide is between those who think human value is extrinsic (and many would add, subjective) and those who think human value is intrinsic and objective. Put another way, bioethicists are divided between the liberals who think human value is based on doing (extrinsic value) and conservatives who think human value is based on being (intrinsic value). Whereas liberals only value the functional expression of certain human capacities, conservatives value the being who possesses those innate capacities whether they are being expressed or not.
To Each His Own Burden
Liberal bioethicists who value the expression of certain human capacities need to explain why anyone else should agree with them that value resides in the functional expression of certain capacities rather than the possession of the capacities themselves. They also need to explain why the particular functions they identify as value-laden should be thought to have actual value. Why not some other set of functions? Indeed, why value any human functions at all?
Likewise, conservative bioethicists who value humans qua humans with their innate capacities need to explain what it is that makes humans actually valuable. On this point, conservative bioethicists are divided. Some argue that the existence of God is necessary to ground objective and intrinsic human value, while others think such a notion can be defended independent of the God question. Those who argue that the existence of God is not necessary to ground human exceptionalism typically argue for the objective, intrinsic moral value of human beings based on our exceptional abilities and moral capacities. While our amazing abilities and superior capacities certainly provide us with good reason to think we are special in the animal kingdom and should be treated differently from other animals, this does nothing to establish that our value is intrinsic and objective.
Even liberal bioethicists generally agree that humans are unique and special – and that we should be treated as such – but on their account human value is subjective and extrinsic. It is extrinsic because value resides in particular functions humans exhibit, not in the human person himself (or our natural capacity to express those functions). And it is subjective because it is humans who choose to value functions X, Y, and Z. In and of themselves, X, Y, and Z are just as valueless as A, B, and C, but because we find utilitarian value in X, Y, and Z, we invest them with value. If humans did not assign value to those functions, then they would lack value.
Conservative bioethicists who argue for human exceptionalism without reference to God, then, need to explain why our innate possession of various capacities such as moral agency, creativity, and rationality are morally and objectively valuable, such that anyone who has or exercises those capacities is valuable. What is the objective basis for making those the things that are objectively valuable? Where did they get your value-defining capacities list from, and why should anyone else adopt it as opposed to some other list or even no list at all?
It seems to me that if value is objective (real), then it must have a source that transcends human opinion. If X, Y, and Z are valuable only because we think they are, then their value is entirely subjective. To make sense of objective, intrinsic human value one must appeal to a source transcendent to human beings, from which humans derive their value. What is that source if not God?
While I think all conservatives and even liberal bioethicists can agree that we can apprehend the moral worth of human beings independent of belief in God (a deliverance of epistemology), the existence of God is necessary to make sense of objective human value (a deliverance of ontology). Apart from the existence of a God that made us in His image, there is no way to elevate human value beyond the instrumental and subjective. There can be no objective, intrinsic value apart from a transcendent Valuer who is intrinsically valuable, and from whom we derive value. If there is no transcendent Valuer of human beings such that they have value in virtue of the kind of beings they are, then there is no reason to value humans qua humans and there is no reason to value our capacity for X, Y, and Z rather than valuing the mere expression of X, Y, and Z. While one does not need to embrace theism to recognize human value, one does need to embrace theism to explain that which he recognizes.