9. But I am afraid I have still not removed the chief difficulty which may prevent acceptance of the proposition that good is indefinable. I do not mean to say that the good, that which is good, is thus indefinable; if I did think so, I should not be writing on Ethics, for my main object is to help towards discovering that definition. It is just because I think there will be less risk of error in our search for a definition of “the good,” that I am now insisting that good is indefinable. I must try to explain the difference between these two. I suppose it may be granted that “good” is an adjective. Well “the good,” “that which is good,” must therefore be the substantive to which the adjective “good” will apply: it must be the whole of that to which the adjective will apply, and the adjective must always truly apply to it. But if it is that to which the adjective will apply, it must be something different from that adjective itself; and the whole of that something different, whatever it is, will be our definition of the good. Now it may be that this something will have other adjectives, beside “good,” that will apply to it. It may be full of pleasure, for example; it may be intelligent: and if these two adjectives are really part of its definition, then it will certainly be true, that pleasure and intelligence are good. And many people appear to think that, if we say “Pleasure and intelligence are good,” or if we say “Only pleasure and intelligence are good,” we are defining “good.” Well, I cannot deny that propositions of this nature may sometimes be called definitions; I do not know well enough how the word is generally used to decide upon this point. I only wish it to be understood that that is not what I mean when I say there is no possible definition of good, and that I shall not mean this if I use the word again. I do most fully believe that some true proposition of the form “Intelligence is good and intelligence alone is good” can be found; if none could be found, our definition of the good would be impossible. As it is, I believe the good to be definable; and yet I still say that good itself is indefinable.
10. “Good,” then, if we mean by it that quality which we assert to belong to a thing, when we say that the thing is good, is incapable of any definition, in the most important sense of that word. The most important sense of “definition” is that in which a definition states what are the parts which invariably compose a certain whole; and in this sense “good” has no definition because it is simple and has no parts. It is one of those innumerable objects of thought which are themselves incapable of definition, because they are the ultimate terms by reference to which whatever is capable of definition must be defined. That there must be an indefinite number of such terms is obvious, on reflection; since we cannot define anything except by an analysis, which, when carried as far as it will go, refers us to something, which is simply different from anything else, and which by that ultimate difference explains the peculiarity of the whole which we are defining: for every whole contains some parts which are common to other wholes also. There is, therefore, no intrinsic difficulty in the contention that “good” denotes a simple and indefinable quality. There are many other instances of such qualities.
Consider yellow, for example. We may try to define it, by describing its physical equivalent; we may state what kind of light-vibrations must stimulate the normal eye, in order that we may perceive it. But a moment’s reflection is sufficient to show that those light-vibrations are not themselves what we mean by yellow. They are not what we perceive. Indeed we should never have been able to discover their existence, unless we had first been struck by the patent difference of quality between the different colours. The most we can be entitled to say of those vibrations is that they are what corresponds in space to the yellow which we actually perceive.
Yet a mistake of this simple kind has commonly been made about “good.” It may be true that all things which are good are also something else, just as it is true that all things which are yellow produce a certain kind of vibration in the light. And it is a fact, that Ethics aims at discovering what are those other properties belonging to all things which are good. But far too many philosophers have thought that when they named those other properties they were actually defining good; that these properties, in fact, were simply not
