ed Unextended
| (e.g., Pleasure and Pain)
|
----------------
| |
Resistant Not-resistant
(Matter) (Space)
|
-------------------
| |
Gravitating Not-gravitating
|
-----------
| |
Simple Compound

Having subdivided 'Simple' by all possible characters, we must then go
back and similarly subdivide Not-phenomenal, Unextended, Not-resistant,
Not-gravitating, and Compound. Now, if we knew all possible characters,
and the order of their importance, we might prepare _a priori_ a
classification of all possible things; at least, of all things that come
under the principles of Contradiction and Excluded Middle. Many of our
compartments might contain nothing actual; there may, for example, be
nothing that is not phenomenal to some mind, or nothing that is extended
and not-resistant (no vacuum), and so forth. This would imply a breach
of the rule, that the dividing quality be not common to the whole class;
but, in fact, doubts have been, and are, seriously entertained whether
these compartments are filled or not. If they are not, we have concepts
representing nothing, which have been generated by the mere force of
grammatical negation, or by the habit of thinking according to the
principle of Excluded Middle; and, on the strength of these empty
concepts, we have been misled into dividing by an attribute, which
(being universal) cannot be a _fundamentum divisionis_. But though in
such a classification places might be empty, there would be a place for
everything; for whatever did not come into some positive class (such as
Gravitating) must fall under one of the negative classes (the 'Nots')
that run down the right-hand side of the Table and of its subdivisions.

This is the ideal of classification. Unfortunately we have to learn what
characters or attributes are possible, by experience and comparison; we
are far from knowing them all: and we do not know the order of their
importance; nor are we even clear what 'important' means in this
context, whether 'widely prevalent,' or 'ancient,' or 'causally
influential,' or 'indicative of others.' Hence, in classifying actual
things, we must follow the inductive method of beginning with
particulars, and sorting them according to their likeness and difference
as dis