Human dignity is not a human right. Instead, it is a quality that all human beings have in common. It is the reason why human beings have human rights.
Human dignity is what sets human beings off against, and makes them incommensurably more valuable than, all other creatures. For religious believers, human dignity is due to the fact that man was not only created by God, but that he was created in God’s likeness. For Christians, it is due to the fact that God gave his only Son to redeem man fallen into sin; the value of each single human person is thus that of someone for whom Christ was willing to suffer and die. In the Roman Catholic Church up to 1969 in every Holy Mass there was an explicit reference to human dignity:
Deus, qui humanae substantiae dignitatem mirabiliter condidisti, et mirabilius reformasti…
For many centuries these words were proffered by every priest, and listened to by the faithful, every day during Holy Mass, and it must be assumed that it is from there that our understanding of human dignity has entered into the collective moral conscience.
For non-believers and believers alike, human dignity is grounded on the fact that human beings are endowed with moral reason, which enables them to discern and choose between good and evil, and thus to be morally responsible for their actions and ommissions.
As a result of this, human dignity not only means that man has rights, but also that he has obligations: he must be treated in a way that respects his dignity, but he also must not act in a way that is below his dignity.
In ancient Rome, dignitas was the status enjoyed by a man of great merits, or by someone who occupied a high-ranking office. Such a man would be treated with great respect and enjoy many privileges – but if he failed to act in a way that corresponded to his dignity, he risked losing both.
A just legal and political order is an order that respects and protects human dignity. It does so in two different ways. On the one hand, it protects man against violations of his dignity, while on the other hand it teaches and enables him to feel and behave in accordance with his dignity. However, given that an act can be good only if it is freely chosen, it will not unnecessarily restrict freedom. Without freedom, man would function like a machine; i.e., he could not commit any acts of moral value.
A just legal order will therefore never compel someone to do good, but only provide him with the freedom that enables him to do good. It will not prohibit and sanction every evil action, but only those which cannot be tolerated without seriously undermining peace and order.
For a legal order to be correspond to human dignity, it is therefore necessary to respect Natural Law.