The question of the distinction of sins in species is the question: What sin was committed? The question of the distinction in number is the question: How many times was it committed? The theoretical discussion of these questions could be very complicated and will not be undertaken here. However, these questions have a certain practical importance, since Catholics are obliged, as the Council of Trent definitively teaches, to confess mortal sins not only in general—“I have sinned mortally”—but in species and number (see DS 1679/899, 1707/917). Therefore, I treat these questions from this practical point of view.¹³

Sins differ in species not by the difference in external behavior but by the difference in the intelligible aspects of the human act which are defective and so render the act evil. It follows that details of a sin which involve proper names, places, and times do not alter its species.

Generally, penitents will have been instructed to consider certain kinds of acts mortally sinful by being taught a set of specific moral norms. For example, a penitent will have learned that adultery and theft are mortal sins and will confess in these terms. What is fundamentally morally relevant about sins is the precise goods which are violated and the modes of responsibility in respect to which they are violated. However, penitents do not think in these categories and cannot be expected to do so.

Penitents might need help in reaching a reasonably adequate specification of their confession. Confessors should provide such help, not only to fulfill the requirement for integral confession, but also to provide a reasonable basis for instructing and counseling the penitent.

For example, sins of adultery differ specifically according to whether both parties to the adultery are married or only one is married. The appropriate advice to be given also might be somewhat different. Similarly, sins of theft differ in species according to the likely injury which will accrue to the person whose property is stolen; the confessor’s guidance about the duty of restitution also requires more information than the generic indication that theft was committed.

Perhaps the penitent has an erroneously strict conscience which needs to be corrected; such correction will not be given if the confession is permitted to stand at a level of vague generalities. Moreover, no helpful guidance can be given about avoiding occasions of sin without an adequately specific confession. In any case, while the sincere contrition of the penitent and genuine purpose of amendment are far more important than the details of sins, the Church’s clear and definitive teaching about the requirement for specific confession must not be ignored.

From a theoretical point of view, moral acts are individuated by actuations of the will—by choices and by acts of willing implementing prior choices. Thus, the act of machine-gunning fifty persons is one homicide if it carries out a single choice; the complex act of kidnapping might involve dozens of distinct morally evil acts if it requires dozens of distinct choices and acts of executive willing.

In practice, penitents generally count sins by counting external performances, whose individuation is by standards used by common sense. Such an estimation ordinarily can be taken as adequate to fulfill the requirement of integral confession. Moreover, in many cases a penitent can only guess at the frequency with which a certain sin was committed; an estimate of the instances per unit of time over a certain period is sufficient—for example, “about three times a year for the last ten years.”

If a penitent seems to need help to make a judgment concerning the number of sins, the point to keep in mind is that quantity or extent is what is at stake here. Thus, a person involved in a prolonged adulterous relationship should confess the duration of the relationship as well as the approximate frequency of specific acts; a person involved in drug traffic should estimate the volume of business and the number of persons probably harmed; a person who neglected to help support aged parents should indicate the duration of the neglect and the portion of support which was omitted.

In the case of purely internal sins, penitents are likely to count the episodes or discontinuous periods of sin; strictly speaking, the number of sins is determined by the number of immoral choices and subsequent implementing will actuations. Generally, many such sins are committed in the course of any complex act, but if the complex proceeds to an external performance, the penitent ordinarily does not distinguish the numerous sins involved. Nor need such distinctions be pressed; an honest estimate of the extent of sin according to common criteria is sufficient.

A point to notice is that the obligation to be specific and precise in confession is an affirmative one; as such it is limited by one’s reasonable ability to fulfill it. Thus, penitents are held only to examine their consciences with due care and to confess truthfully according to their ability. In exceptional circumstances, where a penitent cannot confess with precision because of a handicap, a language barrier, unavoidable lack of privacy, or simply lack of time (for example, in a disaster situation), then the requirement for specific confession does not hold; the sacrament can be completed without it, although a person absolved under such exceptional circumstances must make good the confession of sins when an opportunity presents itself.