of course, simple. Take any genus:
divide it into two classes, one of which has and the other has not a
certain mark. The two classes must be mutually exclusive and together
exhaustive. Repeat the operation upon each of the classes and continue
the process as long as desired.[371] At every step you thus have a
complete enumeration of all the species, varieties, and so on, each of
which excludes all the others. No mere logic, indeed, can secure the
accuracy and still less the utility of the procedure. The differences
may be in themselves ambiguous or irrelevant. If I classify plants as
'trees' and 'not trees,' the logical form is satisfied: but I have still
to ask whether 'tree' conveys a determinate meaning, and whether the
distinction corresponds to a difference of any importance. A perfect
classification, however, could always be stated in this form. Each
species, that is, can be marked by the presence or absence of a given
difference, whether we are dealing with classes of plants or actions:
and Bentham aims at that consummation though he admits that centuries
may be required for the construction of an accurate classification in
ethical speculations.[372] He exaggerates the efficiency of his method,
and overlooks the tendency of tacit assumptions to smuggle themselves
into what affects to be a mere enumeration of classes. But in any case,
no one could labour more industriously to get every object of his
thought arranged and labelled and put into the right pigeon-hole of his
mental museum. To codify[373] is to classify, and Bentham might be
defined as a codifying animal.

Things thus present themselves to Bentham's mind as already prepared to
fit into pigeon-holes. This is a characteristic point, and it appears in
what we must call his metaphysical system. 'Metaphysics,' indeed,
according to him, is simply 'a sprig,' and that a small one, of the
'branch termed Logic.'[374] It is merely the explanation of certain
general terms such as 'existence,' 'necessity,' and so forth.[375] Under
this would apparently fall the explanation of 'reality' which leads to a
doctrine upon which he often insists, and which is most implicitly given
in the fragment called _Ontology_. He there distinguishes 'real' from
'fictitious entities,' a distinction which, as he tells us,[376] he
first learned from d'Alembert's phrase _Etres fictifs_ and which he
applies in his _Morals and Legislation_. 'Real entities,' according to
him,[377] are 'indi