(b) The law becomes harmful or useless with reference to the lawgiver’s purpose privately or temporarily, if the harm or uselessness affects only individuals, or is not lasting. In this case the law continues to be an instrument of public welfare, or is only momentarily deprived of its beneficial character. Hence it endures; but for temporary inconvenience to the public a remedy is had in suspension of the law, for inconvenience to individuals in dispensation. Example: If the use of fats or grease were forbidden on days of abstinence, and if for a time only it were impossible to obtain the substitutes for the preparation of the food, the law would not cease, but would be suspended until such time as substitutes could be obtained. 503. The inconvenience caused to individuals from the fact that a law does not serve its purpose in a case before them, does not always justify the use of _epieikeia_. (a) If the observance of the law would be detrimental to the purpose intended by the lawgiver, _epieikeia_ might be used; for the lawgiver does not intend that his law should be an obstacle to what he has in view as its end. Example: Caius needs to read a book placed on the Index in order to defend the Faith against attacks, but he is unable to request the general faculty to read forbidden works. Obedience to the law in this case would defeat the purpose of the law, which is the protection of faith, and hence Caius may use epieikeia. (b) If the observance of the law would be unnecessary, but not detrimental as regards the purpose of the lawgiver, _epieikeia_ may not be used; else the law would lose its force through the judgments of individuals in their own favor, and the common welfare would suffer. Examples: Titus has an opportunity to read a book placed on the Index, but has not the time to apply for permission. The work was condemned as dangerous to faith; but Titus is strong in faith, and wishes only to study the literary qualities of the writer. Sempronius, a parish priest, is requested to officiate at a marriage immediately, without proclaiming the banns or seeking a dispensation from proclamation. The purpose of the law of banns is that impediments may be detected and invalid marriages avoided, and Sempronius is absolutely certain that there is no impediment in the case before him. Titus and Sempronius must observe the law, and the same must be said as regards every actual case in which there is the possibility of self-deception and peril to the common good. The theoretical case, in which neither of these inconveniences would be present, need not be considered. 504. The purpose of the law ceases to exist as follows: