An introductory text-book of logic - Mellone, Sydney - Rare Books at ...

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become a
"
DEFINITION.
"
wild animal
: without them he is not a
man. The essential qualities, again, are those from
which the largest number of others may be seen to flow
as consequences. Thus our distinction is between
"essential" and "derived" qualities. And in formulat
ing the rule, we spoke of the
"
"
most essential features ;
for with the progress of knowledge we may find that
some qualities which were supposed to be primary and
essential, turn out to be only derivative.
(2) The term expressing the definition must be
simply convertible with the term defined, neither too
wide nor too narrow.
This rule prevents the definition from being too wide
e.g., to define X as AB, when there are some AB
which are not X, is too wide, and the definition is not
convertible, for it is not true that every AB is X.
Examples :
"
Eloquence is the power of influencing the
feelings by speech or writing." Many things,
said or
written, influence the feelings, but are not eloquent.
"
Virtue is the capacity for ruling over men." Many
who can rule over men are not virtuous.
" The cause
of anything is the antecedent which it invariably
"
follows
"
invariably antecedent
"
(Hume). But the
is not always the cause, though
the constant con
nection of two events may show that they both depend
on the same cause (e.g., day and night). A definition
which is too narrow may be described as the definition
of a higher class by a lower which is included in it, a
"
Wealth consists of
Wealth consists of natural products." The
genus by a species. Examples :
money."
"
student of Economics will recognise these errors, each of
which is a case of a fatally narrow definition.
"
Justice
is minding one s own business." Even if we put a large
interpretation on the term
"
business," and understand