The subject of the present chapter is, then, ethical theories which declare that no intrinsic value is to be found except in the possession of some one natural property, other than pleasure; and which declare this because it is supposed that to be good means to possess the property in question. Such theories I call Naturalistic. I have thus appropriated the name Naturalism to a particular method of approaching Ethics—a method which, strictly understood, is inconsistent with the possibility of any Ethics whatsoever. This method consists in substituting for good some one property of a natural object or of a collection of natural objects; and in thus replacing Ethics by some one of the natural sciences. In general the science thus substituted is one of the sciences specially concerned with man, owing to the general mistake (for such I hold it to be) of regarding the matter of Ethics as confined to human conduct. In general, Psychology has been the science substituted, as by J.S. Mill; or Sociology, as by Professor Clifford, and other modern writers. But any other science might equally well be substituted. It is the same fallacy which is implied, when Professor Tyndall recommends us to conform to the laws of matter: and here the science which is proposed to substitute for Ethics is simply Physics. The name then is perfectly general; for, no matter what the something is that good is held to mean, the theory is still Naturalism. Whether good be defined as yellow or green or blue, as loud or soft, as round or square, as sweet or bitter, as productive of life or productive of pleasure, as willed or desired or felt: whichever of these or of any other object in the world, good may be held to mean, the theory, which holds it to mean them, will be a naturalistic theory. I have called such theories naturalistic because all of these terms denote properties, simple or complex, of some simple or complex natural object; and, before I proceed to consider them, it will be well to define what is meant by nature and by natural objects. (§ 26 ¶ 1)

By nature, then, I do mean and have meant that which is the subject-matter of the natural sciences and also of psychology. It may be said to include all that has existed, does exist, or will exist in time. If we consider whether any object is of such a nature that it may be said to exist now, to have existed, or to be about to exist, then we may know that that object is a natural object, and that nothing, of which this is not true, is a natural object. Thus, for instance, of our minds we should say that they did exist yesterday, that they do exist to-day, and probably will exist in a minute or two. We shall say that we had thoughts yesterday, which have ceased to exist now, although their effects may remain: and in so far as those thoughts did exist, they too are natural objects. (§ 26 ¶ 2)

There is, indeed, no difficulty about the objects themselves, in the sense in which I have just used the term. It is easy to say which of them are natural, and which (if any) are not natural. But when we begin to consider the properties of objects, then I fear the problem is more difficult. Which among the properties of natural objects are natural properties, and which are not? For I do not deny that good is a property of certain natural objects: certain of them, I think, are good; and yet I have said that good itself is not a natural property. Well, my test for these too also concerns their existence in time. Can we imagine good as existing by itself in time, and not merely as a property of some natural object? For myself, I cannot so imagine it, whereas with the greater number of properties of objects—those which I call the natural properties—their existence does seem to me to be independent of the existence of those objects. They are, in fact, rather parts of which the object is made up than mere predicates which attach to it. If they were all taken away, no object would be left, not even a bare substance: for they are in themselves substantial and give to the object all the substance that it has. But this is not so with good. If indeed good were a feeling, as some would have us believe, then it would exist in time. But that is why to call it so is to commit the naturalistic fallacy. It will always remain pertinent to ask, whether the feeling itself is good; and if so, then good cannot itself be identical with any feeling. (§ 26 ¶ 3)