These relations between the three properties just distinguished may be illustrated by references to a whole of the kind from which the name organic was derived—a whole which is an organism in the scientific sense—namely the human body. (§ 21 ¶ 1)

(1) There exists between many parts of our body (though not between all) a relation which has been familiarised by the fable, attributed to Menenius Agrippa, concerning the belly and its members. We can find it in parts such that the continued existence of one is a necessary condition for the continued existence of the other; while the continued existence of this latter is also a necessary condition for the continued existence of the former. This amounts to no more than saying that in the body we hve instances of two things, both enduring for some time, which have a relation of mutual causal dependence on one another—a relation of reciprocity. Frequently no more than this is meant by saying that the parts of the body form an organic unity, or that they are mutually means and ends to one another. And we certainly have here a striking characteristic of living things. But it would be extremely rash to assert that this relation of mutual causal dependence was only exhibited by living things and hence was sufficient to define their peculiarity. And it is obvious that of two things which have this relation of mutual dependence, neither may have intrinsic value, or one may have it and the other lack it. They are not necessarily ends to one another in any sense except that in which end means effect. And moreover it is plain that in this sense the whole cannot be an end to any of its parts. We are apt to talk of the whole in contrast to one of its parts, when in fact we mean only the rest of the parts. But strictly the whole must include all its parts and no part can be a cause of the whole, because it cannot be a cause of itself. It is plain, therefore, that this relation of mutual causal dependence implies nothing with regard to the value of either of the objects which have it; and that, even if both of them happen also to have value, this relation between them is one which cannot hold between part and whole. (§ 21 ¶ 2)

But (2) it may also be the case that our body as a whole has a value greater than the sum of values of its parts; and this may be what is meant when it is said that the parts are means to the whole. It is obvious that if we ask the question Why should the parts be such as they are? a proper answer may be Because the whole they form has so much value. But it is equally obvious that the relation which we thus assert to exist between part and whole is quite different from that which we assert to exist between part and part when we say This part exists, because that one could not exist without it. In the latter case we assert the two parts to be causally connected; but, in the former, part and whole cannot be causally connected and the relation which we assert to exist between them may exist even though the parts are not causally connected either. All the parts of a picture do not have that relation of mutual causal dependence, which certain parts of the body have, and yet the existence of those which do not have it may be absolutely essential to the value of the whole. The two relations are quite distinct in kind, and we cannot infer the existence of the one from that of the other. It can, therefore, serve no useful purpose to include them both under the same name; and if we are to say that a whole is organic because its parts are (in this sense) means to the whole, we must not say that it is organic because its parts are causally dependent on one another. (§ 21 ¶ 3)