Musicians
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Classical            Not-classical
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German    Not-German    German    Not-German

Here no Musician will be found in two classes, unless he has written works in two styles, or unless there are works whose style is undecided.  This “unless—­or unless” may suggest caution in using dichotomy as a short cut to the classification of realities.

4.  No Sub-class must include anything that is not comprised in the class to be divided:  the Genus comprises all the Species.  We must not divide Dogs into fox-terriers and dog-fish.

Sec. 6.  The process of Inductive Classification may be represented thus: 

Given any multitude of individuals to be classified: 

(1) Place together in groups (or in thought) those things that have in common the most, the most widely diffused and the most important qualities.

(2) Connect those groups which have, as groups, the greater resemblance, and separate those that have the greater difference.

(3) Demarcate, as forming higher or more general classes, those groups of groups that have important characters in common; and, if possible, on the same principle, form these higher classes into classes higher still:  that is to say, graduate the classification upwards.

Whilst in Division the terms ‘Genus’ and ‘Species’ are entirely relative to one another and have no fixed positions in a gradation of classes, it has been usual, in Inductive Classification, to confine the term ‘Species’ to classes regarded as lowest in the scale, to give the term ‘Genera’ to classes on the step above, and at each higher step to find some new term such as ‘Tribe,’ ‘Order,’ ‘Sub-kingdom,’ ‘Kingdom’; as may be seen by turning to any book on Botany or Zoology.  If, having fixed our Species, we find them subdivisible, it is usual to call the Sub-species ‘Varieties.’

Suppose an attempt to classify by this method the objects in a sitting-room.  We see at a glance carpets, mats, curtains, grates, fire-irons, coal-scuttles, chairs, sofas, tables, books, pictures, musical instruments, etc.  These may be called ‘Species.’  Carpets and mats go together; so do chairs and sofas; so do grates, fire-irons, and coal-scuttles and so on.  These greater groups, or higher classes, are ‘Genera.’  Putting together carpets, mats and curtains as ‘warmth-fabrics’; chairs, sofas and tables as ‘supports’; books, pictures and musical instruments as ‘means of culture’; these groups we may call Orders.  Sum up the whole as, from the housewife’s point of view, ‘furniture.’  If we then subdivide some of the species, as books into poetry, novels, travels, etc., these Sub-species may be considered ‘Varieties.’