Almost everyone agrees that we ought to respect persons. They think we ought to do so because persons are not "things" that can be disposed of at will. They regard them as beings of moral worth, with a dignity that ought to be respected by others and endowed with rights that ought to be recognized and protected by civil authority. Surely almost all Americans make their own the "self-evidence of the truth" affirmed in the Declaration of Independence that "[all men] are endowed by their Creator with certain unalienable rights, that among these rights are Life, Liberty, and the pursuit of Happiness."
Most people believe that human persons, unlike things or other animals, have a moral conscience and make judgments about their own freely-chosen acts, both before and after they act. All of us know that we frequently regret some things we chose to do and that, at times, we experience remorse over what we have done; and there is a crucial moral difference between regret and remorse. When we regret an act, we realize that at the time we chose to do it we did not realize that it was something we ought not to have done. For instance, we may have blamed a friend to whom we had loaned our lawn mower for having damaged it when in fact he had not. In such instances, the proper response is to apologize and to learn to take care of getting facts straight before accusing anyone of doing us wrong.
Remorse is quite different. When we experience remorse, we realize that at the time we did what we chose to do, we knew that we ought not to do it but did it nonetheless. For instance, when we lied to a friend by telling him we had written a letter he had asked us to write recommending him for a job and had not written the letter, remorse is an appropriate reaction and should lead us to repent of our deed and beg our friend's forgiveness.
A moral conscience and such experiences as regret and remorse characterize the existence of human persons. Dogs, cats, chimpanzees, gorillas and other non-human animals do not have a moral conscience nor then do we hold them morally responsible for their actions.
Precisely because we have a moral conscience, all of us - all human persons - know that we ought to seek the truth and to shape our choices and our lives in accordance with it. This in fact is one kind of dignity proper to man, to human persons: the dignity that they are called to give to themselves as moral agents. We can truly say that all men have in their hearts a "law" written by God. Because the term "law" has legalistic interpretations and suggests something imposed on us by some extrinsic authority, it is better and in many ways far more accurate to speak of God's "loving plan for human existence." We have in our hearts a "plan" for our existence and that of our fellow man. It is also true to say that it is in accord with man's dignity to obey this "plan," according to which he will be judged. Man's conscience is rightly called "the most secret core and sanctuary of a man where he is alone with God, whose law echoes in his depths."[1]
Human dignity, however, is an endowment, not an achievement, and it can never be lost because it is rooted in the very being of the person. Moreover, all human persons, all men and women, are endowed with this dignity, from the moment their life begins, from their very creation by God in his own image and likeness. "Let us make man to our own image, after our likeness…." God created man in his own image; in the divine image he created them, male and female he created them (Gen 1: 26, 27).
This brings us to the root dignity of the person and the source of this dignity. The dignity of the human person central to moral dignity is an acquired dignity, not an endowment. Once acquired, it can also be lost when persons choose not to conform to moral truth. And not all persons have this moral dignity; it is a dignity they are called upon to give to themselves. Moreover they are "equipped" to give themselves this dignity because by using their minds they can come to the knowledge of the truth and by exercising their wills can determine themselves morally in and through the choices they make every day of their lives. Acquiring moral dignity, in addition, can be hindered or helped by what we can call "disabling" and "enabling factors." Disabling factors include our own sinful choices, those cultural mores based on the failings and sins of different cultures, and ultimately original sin. Enabling factors include our own good moral choices and deeds, the truths mediated to us by our parents and the culture in which we live, and ultimately by God himself, our best and wisest friend who, if we ask him, will give the help we need to acquire this dignity.
Our Creator, God alone, in whose image and likeness human persons have been created, is the source of the human person's endowed dignity as beings made in his image. He is also the ultimate source of the human person's moral dignity and of the moral order. He is so because he has in fact enabled us, precisely as persons made in his image and likeness, capable of personally participating in his "plan of wisdom and love," his eternal "law." We do so through the "natural law" written into our hearts. And it is through the mediation of our conscience that this "law," our personal and intelligent participation in God's loving plan for human existence, becomes known to us.
Much more can be said about the dignity of human persons, but this may serve as a basic understanding.