3. And the _likeness_, or _unlikeness_, _equality_, or _inequality_ of one body to another, is called their RELATION; and the bodies themselves _relatives_ or _correlatives_; _Aristotle_ calls them τὰ πρὸς τί; the first whereof is usually named the _antecedent_, and the second the _consequent_; and the _relation_ of the antecedent to the consequent, according to magnitude, namely, the equality, the excess or defect thereof, is called the PROPORTION of the antecedent to the consequent; so that _proportion_ is nothing but the equality or inequality of the magnitude of the antecedent compared to the magnitude of the consequent by their difference only, or compared also with their difference. For example, the _proportion_ of three to two consists only in this, that three _exceeds_ two by unity; and the proportion of two to five in this, that two, compared with five, is _deficient_ of it by three, either simply, or compared with the numbers different; and therefore in the proportion of unequals, the proportion of the less to the greater, is called DEFECT; and that of the greater to the less, EXCESS. [Sidenote: Proportionals, what.] 4. Besides, of unequals, some are more, some less, and some equally unequal; so that there is _proportion of proportions_, as well as of _magnitudes_; namely, where two unequals have relation to two other unequals; as, when the inequality which is between 2 and 3, is compared with the inequality which is between 4 and 5. In which comparison there are always four magnitudes; or, which is all one, if there be but three, the middlemost is twice numbered; and if the proportion of the first to the second, be equal to the proportion of the third to the fourth, then the four are said to be _proportionals_; otherwise they are not proportionals. [Sidenote: The proportion of magnitudes to one another, wherein it consists.] 5. The proportion of the antecedent to the consequent consists in their difference, not only simply taken, but also as compared with one of the relatives; that is, either in that part of the greater, by which it exceeds the less, or in the remainder, after the less is taken out of the greater; as the proportion of two to five consists in the three by which five exceeds two, not in three simply only, but also as compared with five or two. For though there be the same difference between two and five, which is between nine and twelve, namely three, yet there is not the same inequality; and therefore the proportion of two to five is not in all relation the same with that of nine to twelve, but only in that which is called arithmetical. [Sidenote: Relation is no new accident, but one of those that were in the relative, before the relation or comparison was made. Also the causes of accidents in correlatives are the cause of relation.]