When an entrusted secret, however, which is also called a strict or absolutely natural secret, is imparted expressly or tacitly, say, to physicians, lawyers, or priests, and becomes a professional secret, it obliges more strictly than any other. There are four conditions under which such an entrusted secret may be revealed, at least without mortal sin (except by a confessor): (1) If we have the presumed consent of the principal. (2) If the material of the secret is trivial, or if it is known from another source, or is already public. Is it a mortal sin to divulge a grave entrusted secret to a responsible person who is under the same bond? St. Alphonsus, De Lugo, and others say probably it is not, provided the secret is not divulged to the particular person from whom the principal wished it to be concealed. The term _probably_ here is technical and refers more to the absolute truth of an assertion than to its practical application. (3) One might reveal such a secret without mortal sin, through inadvertence or thoughtlessness, or under the supposition that it is not a grave secret. Some moralists hold, however, that to excuse from mortal sin, the revealer must be certain that the matter of the secret is not grave. (4) Such a secret may be revealed if keeping it would cause public injury, or injury to an innocent person, or injury to the person to whom the secret has been entrusted; then the law of charity demands that it be revealed. Therefore, even if one has bound himself under oath, he may reveal the secret--always excepting a priest or confessor. This is the common doctrine of moral theologians. It is for the common good of human society that entrusted secrets be absolutely kept unless so grave a damage befalls another from such observance that it becomes more conducive to the public good to reveal than to conceal. To let an infective syphilitic, for example, spread his contagion merely because an entrusted secret should be kept is a much greater damage to the public than a good. Barrett[163] says a physician may not divulge the diseases of a family to an insurance company unless the family assents; he may not tell the man before marriage that the woman had been operated upon, say, for ovariotomy, unless the woman gives permission; nor may he let the woman know, before marriage, of those diseases of the man which are not contagious. Ho says further that if a man has had syphilis and is now completely cured, the physician may not reveal this previous condition to the woman. [163] Sabetti-Barrett, _Compend. Theol. Moral._, n. 565. New York, 1915.