(c) If the law contains the following words: _praesumpserit, ausus fuerit, scienter, studiose, temerarie, consulto egerit_, or others similar to them which require full knowledge and deliberation, any diminution of imputability on the part of either the intellect or the will exempts the delinquent from penalties _latae sententiae_ (Canon 2229, Sec.2). (d) If the law does not contain such words, crass or supine ignorance of the law or even of only the penalty does not exempt from any penalty _latae sententiae_; ignorance that is not crass or supine exempts from medicinal penalties, but not from vindicative penalties _latae sententiae_ (Canon 2229, Sec.3, 1).
491. Other specific determinations of the law include: (a) Inculpable ignorance of the law itself excludes moral imputability (Canon 2202, Sec.1); actual inculpable inadvertence or error in regard to the law has the same effect (Canon 2202, Sec.3). (b) Culpable ignorance, or culpable inadvertence, or error concerning the law or concerning the fact diminish imputability more or less in proportion to the culpability of the ignorance (Canon 2202, Sec.1). (c) If the ignorance, even inculpable, affects only the fact of the existence of the penalty, it does not exclude imputability of the delict, but it does diminish it (Canon 2202, Sec.2).
492. Absolute or physical impossibility (i.e., the want of the power or of the means of complying with a law), of course, excuses from its observance; for no one is bound to what is impossible. This applies to divine law, and hence much more to human law. Example: He who is unable to leave the house is not obliged to go to Mass.
493. Moral impossibility—that is, the inability to comply with the law without extraordinary labor, or the imminent danger of losing a notable good or of incurring a great evil—does not excuse from the observance of ecclesiastical law when this law receives through circumstances the added force of the negative law of nature. This happens when the evil that will result through the observance of the law bears no proportion to the evil that will result from its violation, the former being private or temporal or human, the latter public or spiritual or divine; for the law of nature forbids that the common welfare, or the salvation of a soul, or the honor of God be sacrificed for the benefit of an individual, or for the life of the body, or for the welfare of a creature. Example: The command to abstain from meat on Friday obliges, if one has been ordered to violate it as a sign of contempt of God or of religion, even though death is threatened for refusal.
494. Moral impossibility excuses from the observance of a human law in the following cases:
(a) One is excused when a considerable loss in health, reputation, spiritual advantage, property, etc., or a grave inconvenience will result from observing a law which is not a prohibition of nature in the sense of the previous paragraph; for the legislator cannot impose obligations that are needlessly heavy, and hence positive law does not oblige in case of such moral impossibility. Example: Our Lord reproved the inhuman rigor of the Pharisees, who insisted that their regulations must be observed, whatever the difficulty or cost.
(b) One is excused when a lower or less urgent law is in conflict with a law that is higher or more urgent. In such a case the greater obligation prevails, and the lesser obligation disappears. Examples: The divine laws that one must preserve one’s life or administer Baptism to a dying person prevail over the human law of attendance at church. The less urgent law of fasting yields to the more urgent law of devoting oneself to duties required by one’s state of life, if there is a conflict between the two laws.
495. The loss, evil or inconvenience that constitutes moral impossibility with respect to a law, must bear a proportion to the law itself; and hence the higher or the more imperative the law, the greater must be the reason that suffices to excuse from it.
496. Only a learned and prudent man can determine whether moral impossibility exists with reference to a particular case, and hence it would be dangerous for those who are not theologians to decide, either for themselves or for others. The points that have to be considered in judging are: (a) whether or not the difficulty is of a gravity proportionate to the importance of the law (e.g., a graver reason is required to excuse from a law that obliges under mortal sin than to excuse from a law that binds under light sin); (b) whether or not the difficulty is grave in relation to the person concerned (e.g., an obligation that is easy for a healthy person may be very difficult for one who is infirm).
497. It is never lawful to bring about either physical or moral impossibility of observing a law, if this be done with the sole or principal purpose of escaping one’s duty. Example: To go away on Saturday in order to avoid Mass on Sunday.