One can therefore establish three kinds of immoral actions, which can be judged as such by referring to the three basic principles: whether they are immoral either in themselves, or because the person who enacts them lacks the right to do so, or because of the dangers they provoke without sufficient motive.
Actions which are immoral because the person who enacts them has no right to do so, do not in themselves contain any essential immoral element but, if they are to be licit, they must suppose the existence of an explicit or implicit right as will be the case in the majority of instances for the doctor and the psychologist. Since a right cannot be taken for granted, it must first of all be established through positive proof by the person who assumes it and based on a juridical reason. As long as the right has not been obtained, the action is immoral. But if, at a specific time, an action appears to be immoral, it does not still follow that it will always remain such, because it can happen that the right shown to be lacking is acquired later. Nevertheless, the right in question can never be taken for granted. As We said previously, again in this instance, it is up to you to decide in concrete cases, many examples of which are quoted in the publications of your specialization, whether this principle is applicable to such or such an action. Thirdly, certain actions are immoral because of the danger incurred without a proportionate motive. We naturally refer to moral danger for the individual or the community, either regarding the personal property of the body, of life, of reputation, of customs or with respect to material assets. (Papal Writings, 10 April 1958).
2. Therefore there can be no true promotion of man's dignity unless the essential order of his nature is respected. Of course, in the history of civilization many of the concrete conditions and needs of human life have changed and will continue to change. But all evolution of morals and every type of life must be kept within the limits imposed by the immutable principles based upon every human person's constitutive elements and essential relations -- elements and relations which transcend historical contingency. Hence, those many people are in error who today assert that one can find neither in human nature nor in the revealed law any absolute and immutable norm to serve for particular actions other than the one which expresses itself in the general law of charity and respect for human dignity. (Sacred Congregation for the Doctrine of the Faith: Persona Humana, 1975).