(a) Physically, an object is one when it has its own proper individuality different from that of others. Thus, each coin in a pocket-book is physically one thing, each member of a family is physically one person. Objects are physically many, when they include more than one distinct thing or person. Thus, physically a pocket-book contains many objects, as does also a family.
(b) Morally, objects that are physically many become one, if they are not such as to require morally distinct acts in their regard, and if they form according to prudent judgment parts of an integral or collective whole. Otherwise, these objects are morally many. Example: Missing Mass for a whole year constitutes, morally speaking, many objects, since it implies many independent external omissions, or morally distinct acts. A box of ordinary coins, though it contains many individual pieces of money, is commonly regarded as one integral object; and likewise religious, civil, domestic, and financial bodies, though each is made up of many members, are each, morally speaking, but one person. The possessions of different proprietors, however, are not one moral object; neither do the individual, personal rights of the members of one group constitute a single object.
206. It is clear that two sins specifically different in malice are also numerically different (e.g., a sin of theft and a sin of calumny). The rules that follow will pertain only to sins that are of the same species, but that differ numerically within the species (e.g., two distinct sins of theft, two distinct sins of calumny).
207. The rules for the numerical distinction of sins within the same species suppose: (a) that the distinction be not taken from the object, which gives the specific difference, but from the repetition of acts with regard to one object, made either actually (by different acts) or equivalently (by what is equal to different acts); (b) that the distinction be not taken from a physical but from a moral consideration of the acts.
208. Three rules of numerical distinction will be given, one for each of the three following hypotheses: (a) many distinct acts are concerned with morally distinct objects of the same species; (b) many distinct acts are concerned with what is morally one object; (c) one act is concerned with what are physically many, but morally one object.
209. First Rule of Numerical Distinction.—Many sinful acts, each of which is concerned with an object that is distinct in number (morally speaking) from the objects of the other acts, make as many numerically distinct sins as there are acts and objects numerically distinct. Example: He who fires distinct shots and unjustly kills three persons is guilty of three murders.
210. Second Rule of Numerical Distinction.—Many sinful acts, all of which are concerned with an object that is (morally speaking) one and the same in number, make as many numerically distinct sins as there are acts numerically distinct according to moral estimation.
211. When the acts concerned with the same object are purely internal, they are multiplied numerically, according to moral estimation, in the following cases:
(a) when they are repeated after having been renounced by an act of the will. Example: He who hates in the morning, repents at noon, and returns to his hate in the afternoon, commits two sins of hatred;
(b) when they are repeated after having been voluntarily discontinued, if the interval between the two acts is so considerable that the second act is not a mere continuation of the first. Example: He who in his mind reviles an enemy passing by, then turns his attention to his work and thinks no more about his anger, and later, seeing his enemy again, reviles him mentally a second time, commits two sins;