Not only does Wolterstorff trace the origins of the idea of universal human dignity back to early Jewish and Christian moral thinking, but he also makes the striking and controversial claim that without such theistic resources we will be left without any satisfactory grounding for dignity: no secular worldview can do the job. In Kant's ethics, for example, dignity hinges, as we have seen, on the capacity for rational choice; yet if human worth depends on this, then those who lack that capacity (infants, those born with severe mental impairment, Alzheimer's patients) risk being excluded from the domain of rights-holders. If rational choice is the criterion, how can this explain why every human, qua human, should be regarded as having inherent worth?

The Judaeo-Christian idea of the importance of loving one's neighbour may have something to teach us here. A neighbour is someone with whom we enter into relations of vulnerability and dependence, simply in virtue of our shared proximity. To be a friend or neighbour with someone is to be prepared to have one's own space encroached on by them, just as they are reciprocally prepared to receive us. If we were purely rational disembodied agents or mere "persons", in some quasi-Cartesian sense of mere "thinking things" or "conscious beings", true relationships as we understand them would be inconceivable: they would be reduced to detached interchanges of information, interactive exercises of intellection and volition, but without all the vulnerabilities of embodied particularity that make love and friendship truly precious. For in true relations of neighbourliness, friendship and love, we abandon our austere self-sufficient autonomy, and accept our "passivity" (as the Zurich-based philosopher Ingolf Dalferth has put it): we know our need, our dependency, and need it to be recognised by others. And once we know this, we can see at once that our dignity and worth cannot depend on our rational powers and capacities, nor our ability to determine our choices as moral lawgivers, nor any other intellectual endowment, even that of consciousness (which may of course be dormant, or de-activated, as in a coma), but simply and solely on our need for others to reach out to us, as we need to reach out to them. This is a need that applies to every single human being on the planet. To mature morally is to come to realise that we gain nothing by insisting on our status, or "standing on our dignity" (as the English idiom has it), but that we gain everything by recognising the dependency we share with all our neighbours.

This seems to me to be a clear point in favour of the religious account; for why should our human weakness and dependency provide any purely secular reason why dignity or worth should attach to us all simply as human beings? On a standard Darwinian view of human nature, our nature is simply a set of contingent features that have emerged out of a blind nexus of forces, shaped by random mutation and the struggle for survival. So selecting any one of these features, such as our frailty and dependency, as the basis for according inherent worth to us, seems pretty arbitrary, or at any rate no more or less warranted than ascribing true dignity on the basis of heroic intellect and will (following Nietzsche), or aristocratic "great-souledness" (following Aristotle).