of fine art, or of literature, in
politics, religion and moral philosophy, what we are anxious to say is
often far from clear to ourselves; and it is better to indicate our
meaning approximately, or as we feel about it, than to convey a false
meaning, or to lose the warmth and colour that are the life of such
reflections. It is hard to decide whether more harm has been done by
sophists who take a base advantage of the vagueness of common terms, or
by honest paralogists (if I may use the word) who begin by deceiving
themselves with a plausible definiteness of expression, and go on to
propagate their delusions amongst followers eager for systematic insight
but ignorant of the limits of its possibility.

Sec. 3. A Definition is necessary (if possible) for every scientific name.
To define a name is to give a precise statement of its meaning or
connotation. The name to be defined is the subject of a proposition,
whose predicate is a list of the fundamental qualities common to the
things or processes which the subject denotes, and on account of
possessing which qualities this name is given to them.

Thus, a curve is a line of which no part is straight. The momentum of a
moving body is the product of its mass and its velocity (these being
expressed in numbers of certain units). Nitrogen is a transparent
colourless gas, atomic weight 14, specific gravity .9713, not readily
combining, etc. A lion is a monodelphian mammal, predatory, walking on
its toes, of nocturnal habits, with a short rounded head and muzzle;
dental formula: Incisors (3-3)/(3-3), canines (1-1)/(1/1), praemolars
(3-3)/(2-2), molars (1-1)/(1-1) = 30; four toes on the hind and five on
the fore foot, retractile claws, prickly tongue, light and muscular in
build, about 9-1/2 feet from muzzle to tip of tail, tawny in colour, the
males maned, with a tufted tail. If anything answers to this
description, it is called a lion; if not, not: for this is the meaning
of the name.

For ordinary purposes, it may suffice to give an Incomplete Definition;
that is, a list of qualities not exhaustive, but containing enough to
identify the things denoted by the given name; as if we say that a lion
is 'a large tawny beast of prey with a tufted tail.' Such purposes may
also be served by a Description; which is technically, a proposition
mentioning properties sufficient to distinguish the things denoted, but
not the properties that enter into the definition; as if nitrogen be
indic