IV. _The division should be exclusive._ That is, the various species divided from a genus, should be reciprocally exclusive--should exclude one another. Thus to divide _mankind_ into _male_, _men and women_, would be illogical, because the class _male_ includes _men_. The division should be either: "_male and female_;" or else: "men, women, boys, girls." The exercise of Division along these lines, and according to these rules, will tend to improve one's powers of conception and analysis. Any class of objects--any general concept--may be used for practice. A trial will show you the great powers of unfoldment contained within this simple process. It tends to broaden and widen one's conception of almost any class of objects. There are also several rules for Partition which should be observed, as follows: I. _The partition should be complete and exhaustive._ That is, it should unfold the full meaning of the term or concept, so far as is concerned its several general qualities, properties and attributes. But this applies only to the qualities, properties and attributes which are _common_ to the class or concept, and not to the minor qualities which belong solely to the various sub-divisions composing the class; nor to the accidental or individual qualities belonging to the separate individuals in any sub-class. The qualities should be _essential_ and not _accidental_--general, not particular. A famous violation of this rule was had in the case of the ancient Platonic definition of "Man" as: "A two-legged animal without feathers," which Diogenes rendered absurd by offering a plucked chicken as a "man" according to the definition. Clearness in thought requires the recognition of the distinction between the general qualities and the individual, particular or accidental qualities. Red-hair is an accidental quality of a particular man and not a general quality of the class _man_. II. _The partition should consider the qualities, properties and attributes_, according to the classification of logical division. That is, the various qualities, properties and attributes should be considered in the form of genus and species, as in Division. In this classification, the rules of Division apply.