Chapter I: The Subject-Matter of Ethics.
§ 7.
Let us, then,
consider this position. My point is that good
is a simple notion, just as
yellow
is a simple notion; that, just as you cannot, by any manner of
means, explain to anyone who does not already know it, what yellow is, so you
cannot explain what good is. Definitions of the kind that I was asking for,
definitions which describe the real nature of the object or notion denoted by a
word, and which do not merely tell us what the word is used to mean, are only
possible when the object or notion in question is something complex. You can
give a definition of a horse, because a horse has many different properties and
qualities, all of which you can enumerate. But when you have enumerated them
all, when you have reduced a horse to his simplest terms, you can no longer
define those terms. They are simply something which you think of or perceive,
and to anyone who cannot think of or perceive them, you can never, by any
definition, make their nature known. It may perhaps be objected to this that we
are able to describe to others, objects which they have never seen or thought
of. We can, for instance, make a man understand what a chimaera is, although he
has never heard of one or seen one. You can tell him that it is an animal with a
lioness’s head and body, with a goat’s head growing from the middle of its back,
and with a snake in place of its tail. But here the object which you are
describing is a complex object; it is entirely composed of parts, with which we
are all perfectly familiar—a snake, a goat, a lioness; and we know, too, the
manner in which those parts are to be put together, because we know what is
meant by the middle of a lioness’s back, and where her tail is wont to grow. And
so it is with all objects not previously known, which we are able to define:
they are all complex; all composed of parts, which may themselves, in the first
instance, be capable of similar definition, but which must in the end be
reducible to simplest parts, which can no longer be defined. But yellow and
good, we say, are not complex: they are notions of that simple kind, out of
which definitions are composed and with which the power of further defining
ceases. (§ 7 ¶ 1)