§ 391. In dividing a term the first requisite is to fix upon some point wherein certain members of the class differ from others. The point thus selected is called the Fundamentum Divisionis or Basis of the Division. § 392. The basis of the division will of course differ according to the purpose in hand, and the same term will admit of being divided on a number of different principles. Thus we may divide the term 'man,' on the basis of colour, into white, black, brown, red, and yellow; or, on the basis of locality, into Europeans, Asiatics, Africans, Americans, Australians, New Zealanders, and Polynesians; or again, on a very different principle, into men of nervous, sanguine, bilious, lymphatic and mixed temperaments. § 393. The term required to be divided is known as the Totum Divisum or Divided Whole. It might also be called the Dividend. § 394. The classes into which the dividend is split up are called the Membra Dividentia, or Dividing Members. § 395. Only two rules need be given for division-- (1) The division must be conducted on a single basis. (2) The dividing members must be coextensive with the divided whole. § 396. More briefly, we may put the same thing thus--There must be no cross-division (1) and the division must be exhaustive (2). § 397. The rule, which is commonly given, that each dividing member must be a common term, is already provided for under our definition of the process. § 398. The rule that the dividend must be predicable of each of the dividing members is contained in our second rule; since, if there were any term of which the dividend were not predicable, it would be impossible for the dividing members to be exactly coextensive with it. It would not do, for instance, to introduce mules and donkeys into a division of the term horse. § 399. Another rule, which is sometimes given, namely, that the constituent species must exclude one another, is a consequence of our first; for, if the division be conducted on a single principle, the constituent species must exclude one another. The converse, however, does not hold true. We may have a division consisting of mutually exclusive members, which yet involves a mixture of different bases, e.g. if we were to divide triangle into scalene, isosceles and equiangular. This happens because two distinct attributes may be found in invariable conjunction.