INCAPACITÀ. — In moral theology and law, this is the lack of certain conditions necessary for action, such that a subject finds himself unable to perform a particular act. Since the necessity of certain conditions may originate from different sources, a distinction is made between natural incapacity and positive incapacity. Thus, for example, the incapacity to succeed of one not yet conceived is called natural, as is the incapacity to contract Marriage of one who is already bound by a prior Marriage, etc.; on the other hand, the incapacity to succeed of an unworthy person is called positive, as is the incapacity to contract Marriage of one who is bound to the other party by a bond of consanguinity in the 2nd or 3rd degree of the collateral line, etc. Natural incapacities must be established with certainty by natural law; divine-positive incapacities must likewise be established with certainty by Revelation through the teaching of the Church; human positive incapacities must result from an unequivocal provision of human, ecclesiastical, or civil law.
General capacity with regard to rights and obligations is a necessary consequence of being a person (v. CAPACITÀ); specific capacity, however, in relation to the rights and obligations arising from or guaranteed by a particular legal system, normally derives from the status of citizen. The general causes that affect a person’s capacity by creating incapacities are: age, sex, origin, domicile, family relationships, rite, physical health, and a criminal conviction. In addition to these general causes, individual legal systems recognize other particular ones. In any event, since incapacity for a particular action represents a diminution of personality, it must not be presumed but must be unequivocally established.
As regards the consequences of actions performed by an incapable person, it is necessary to determine whether they take the form of genuine inability or merely of a prohibition. For example, the impediments to Marriage in canon law are incapacities taking the form of inability and, consequently, a Marriage contracted in this way is invalid. Impedient impediments, by contrast, take the form merely of prohibitions and, consequently, a Marriage that may have been contracted remains valid. If the incapacity takes the form of genuine inability, the act performed does not exist and cannot have any consequence; otherwise, the act exists in a condition of irregularity that may entail various consequences, including annulment and rescission. For the practical requirements of a system, it may happen that an act which by its nature is nonexistent (e.g., a contract concluded by a person incapable of understanding and willing: Italian Civil Code, art. 1425) must be regarded as existing and operative until at least the time when it is annulled, giving rise to a genuine conflict between the internal forum and the external forum.