An argument is derived from what has been done, in this way: "When a woman becomes the wife of a man, everything which has belonged to the woman now becomes the property of the husband under the name of dowry."
But in the way of comparison there are many kinds of valid arguments; in this way: "That which is valid in a greater affair, ought to be valid in a less: so that, if the law does not regulate the limits in the city, still more will it not compel any one to turn off the water in the city." Again, on the other hand: "Whatever is valid in a smaller matter ought to be valid also in a greater one. One may convert the preceding example." Also, "That which is valid in a parallel case ought to be valid in this which is a parallel case." As, "Since the usurpation of a farm depends on a term of two years, the law with respect to houses ought to be the same." But in the law houses are not mentioned, and so they are supposed to come under the same class as all other things, the property in which is determined by one year's use. Equity then must prevail, which requires similar laws in similar cases.[64]
But those arguments which are derived from external circumstances are deduced chiefly from authority. Therefore the Greeks call argumentations of that kind [Greek: atechuoi], that is, devoid of art. As if you were to answer in this way:—"In the case of some one building a roof for the purpose of covering a common wall, Publius Scaevola asserted that there was no right of carrying that roof so far that the water which ran off it should run on to any part of any building which did not belong to the owner of the roof. This I affirm to be law."
V. By these topics then which have been explained, a means of discovering and proving every sort of argument is supplied, as if they were elements of argument. Have we then said enough up to this point? I think we have, as far at least as you, an acute man and one deeply skilled in law, are concerned. But since I have to deal with a man who is very greedy when the feast in question is one of learning, I will prosecute the subject so that I will rather put forth something more than is necessary, than allow you to depart unsatisfied. As, then, each separate one of those topics which I have mentioned has its own proper members, I will follow them out as accurately as I can; and first of all I will speak of the definition itself.
Definition is a speech which explains that which is defined. But of definitions there are two principal kinds: one, of those things which exist; the other, of those which are understood. The things which I call existing are those which can be seen or touched; as a farm, a house, a wall, a gutter, a slave, an ox, furniture, provisions, and so on; of which kind of things some require at times to be defined by us. Those things, again, I say have no existence, which are incapable of being touched or proved, but which can be perceived by the mind and understood; as if you were to define usucaption, guardianship, nationality, or relationship; all, things which have no body, but which nevertheless have a certain conformation plainly marked out and impressed upon the mind, which I call the notion of them. They often require to be explained by definition while we are arguing about them.
And again, there are definitions by partition, and others by division: by partition, when the matter which is to be defined is separated, as it were, into different members; as if any one were to say that civil law was that which consists of laws, resolutions of the senate, precedents, the authority of lawyers, the edicts of magistrates, custom, and equity. But a definition by division embraces every form which comes under the entire genus which is defined; in this way: "Alienation is the surrender of anything which is a man's private property, or a legal cession of it to men who are able by law to avail themselves of such cession."
VI. There are also other kinds of definitions, but they have no connexion with the subject of this book; we have only got to say what is the manner of expressing a definition. This, then, is what the ancients prescribe: that when you have taken those things which are common to the thing which you wish to define with other things, you must pursue them till you make out of them altogether some peculiar property which cannot be transferred to anything else. As this: "An inheritance is money." Up to this point the definition is common, for there are many kinds of money. Add what follows: "which by somebody's death comes to some one else." It is not yet a definition, for money belonging to the dead can be possessed in many ways without inheritance. Add one word, "lawfully." By this time the matter will appear distinguished from general terms, so that the definition may stand thus:—"An inheritance is money which by somebody's death has lawfully come to some one else." It is not enough yet. Add, "without being either bequeathed by will, or held as some one else's property." The definition is complete. Again, take this:—"Those are gentiles who are of the same name as one another." That is insufficient. "And who are born of noble blood." Even that is not enough. "Who have never had any ancestor in the condition of a slave." Something is still wanting. "Who have never parted with their franchise." This, perhaps, may do. For I am not aware that Scaevola, the pontiff, added anything to this definition. And this principle holds good in each kind of definition, whether the thing to be defined is something which exists, or something which is understood.
VII. But we have shown now what is meant by partition, and by division. But it is necessary to explain more clearly wherein they differ. In partition, there are as it were members; as of a body—head, shoulders, hands, sides, legs, feet, and so on. In division there are forms which the Greeks call [Greek: ideae]; our countrymen who treat of such subjects call them species. And it is not a bad name, though it is an inconvenient one if we want to use it in different cases. For even if it were Latin to use such words, I should not like to say specierum and speciebus. And we have often occasion to use these cases. But I have no such objection to saying formarum and formis; and as the meaning of each word is the same, I do not think that convenience of sound is wholly to be neglected.
Men define genus and species or form in this manner:—"Genus is a notion relating to many differences. Species is a notion, the difference of which can be referred to the head and as it were fountain of the genus." I mean by notion that which the Greeks call sometimes [Greek: ennoia], and sometimes [Greek: enoprolaepsis]. It is knowledge implanted and previously acquired of each separate thing, but one which requires development. Species, then, are those forms into which genus is divided without any single one being omitted; as if any one were to divide justice into law, custom, and equity. A person who thinks that species are the same things as parts, is confounding the art; and being perplexed by some resemblance, he does not distinguish with sufficient acuteness what ought to be distinguished. Often, also, both orators and poets define by metaphor, relying on some verbal resemblance, and indeed not without giving a certain degree of pleasure. But I will not depart from your examples unless I am actually compelled to do so.
Aquillius, then, my colleague and intimate friend, was accustomed, when there was any discussion about shores, (all of which you lawyers insist upon it are public,) to define them to men who asked to whom that which was shore belonged, in this way: "Wherever the waves dashed;" that is, as if a man were to define youth as the flower of a man's age, or old age as the setting of life. Using a metaphor, he departs from the words proper to the matter in hand and to his own art. This is enough as to definition. Let us now consider the other points.