(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 in it parts such that the continued existence of the 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 have 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.