Is all this in fact 'quite clear' and 'quite obvious'? In truth, the one thing that is quite clear and obvious to the Idealist reader is that Mr Moore is working with presuppositions as to the nature of knowledge which his opponents would never dream of admitting. The argument, as stated, simply does not touch Idealism. For what, on Mr Moore's presuppositions, seems 'quite clear,' seems, on Idealist presuppositions, to involve a plain self-contradiction. A very few words should suffice to show that this is so.
Let us consider the proposition 'the red patch has the relational property of being a spatial part in a certain whole.' For convenience we may convert it to the form 'this red patch is present owner of the relational property, etc.,' and then symbolise the subject of the proposition as A and the predicate as B. Now Mr Moore holds that we can accept the proposition 'A is B,' while also accepting the proposition 'A might not have been B.' But this implies, of course, that for Mr Moore the intellect can accept a connection of differents without postulating, much less attempting to explicate, a rational ground for the connection. For it is supposed by Mr Moore that these differences might not have been so united: and such a supposition is incompatible with the postulate of a rational ground for the connection (which implies that the connection, if it is at all, is a necessary connection). In other words, Mr Moore's argument implies the assumption that the intellect does not demand a rationale for its connections, but is prepared to accept a 'bare conjunction' of differents. And this, for the Idealist thinker, e.g. for Bradley, represents the very essence of the self-contradictory - the direct identification of A and not-A. For the Idealist the intellect can assent to the union of A and B only in so far as they are conceived to be mutually implicatory elements within a system X. For him, therefore, it is just nonsense to assert that A is B, and at the same time that A might not have been B.
1 Philosophical Studies, pp. 288-9.
There is no need then for Mr Moore to go on (as he does in the essay from which I have been quoting) to construct an elaborate explanation of the Idealist's obtuseness in failing to recognise the 'obvious fact' that 'in the case of many relational properties which things have... the things in question might have existed without having them.' 1 The explanation is much simpler and much more fundamental than Mr Moore supposes. It is just that the supposed 'obvious fact' is in vital contradiction with the cardinal principle in the Idealist's theory of knowledge. Unless this principle is duly examined and found wanting, attacks upon the doctrine of internal relations are so much beating of the air.
As for the appeal to 'common sense,' the Idealist has never denied that for working purposes certain relational properties may conveniently be treated as external to their terms. And that is all that common sense is concerned with. Reference to common sense yields some indication as to the pragmatical value or disvalue of an idea. But as to ultimate theoretical validity - which is the concern of philosophy - it is no test at all. Those who appeal to it for support on favourable occasions are just as likely to dismiss it with obloquy when its pronouncements happen to be unfavourable.
The Pluralist's attack upon the Idealist doctrine of 'Degrees' seems to me, then, to miss its target through a radical failure to appreciate what are the basic presuppositions upon which the Idealist superstructure is reared. Let us turn now to the Supra-rationalist's criticism - which ought at least to be free from this particular defect.2
1 Philosophical Studies, p. 289.
2 It is, I think, unfortunate that even some Idealist writers have expressed themselves in a way which suggests that they regard the Realist attack upon internal relations as bene fundatum. Thus Mr W. E. Hocking, in his brilliant little book, Types of Philosophy, p. 368 : 'Realism is justified in rebelling against the notion that all relations are "internal." There are external relations, such as make no significant differences to their terms'.