Internal sins
That sin may be committed not only by outward deeds but also by the inner activity of the mind apart from any external manifestation, is plain from the precept of the Decalogue: “Thou shalt not covet”, and from Christ’s rebuke of the scribes and pharisees whom he likens to “whited sepulchres… full of all filthiness” (Matthew 23:27). Hence the Council of Trent (Sess. XIV, c. v), in declaring that all mortal sins must be confessed, makes special mention of those that are most secret and that violate only the last two precepts of the Decalogue, adding that they “sometimes more grievously wound the soul and are more dangerous than sins which are openly committed”. Three kinds of internal sin are usually distinguished:
• delectatio morosa, i.e. the pleasure taken in a sinful thought or imagination even without desiring it;
• gaudium, i.e. dwelling with complacency on sins already committed; and
• desiderium, i.e. the desire for what is sinful.
An efficacious desire, i.e. one that includes the deliberate intention to realize or gratify the desire, has the same malice, mortal or venial, as the action which it has in view. An inefficacious desire is one that carries a condition, in such a way that the will is prepared to perform the action in case the condition were verified. When the condition is such as to eliminate all sinfulness from the action, the desire involves no sin: e.g. I would gladly eat meat on Friday, if I had a dispensation; and in general this is the case whenever the action is forbidden by positive law only. When the action is contrary to natural law and yet is permissible in given circumstances or in a particular state of life, the desire, if it include those circumstances or that state as conditions, is not in itself sinful: e.g. I would kill so-and-so if I had to do it in self-defence. Usually, however, such desires are dangerous and therefore to be repressed. If, on the other hand, the condition does not remove the sinfulness of the action, the desire is also sinful. This is clearly the case where the action is intrinsically and absolutely evil, e.g. blasphemy: one cannot without committing sin, have the desire — I would blaspheme God if it were not wrong; the condition is an impossible one and therefore does not affect the desire itself. The pleasure taken in a sinful thought (delectatio, gaudium) is, generally speaking, a sin of the same kind and gravity as the action which is thought of.