In Chap. VII of the Nature of Existence McTaggart introduces his second indubitable empirical premise, viz., that there is more than one particular. At a much later stage in the book he asserts that every particular has parts which are themselves particulars, and he claims that this can be seen to be a necessary fact. This would, of course entail that, if there were one particular, there would be many, indeed infinitely many, particulars. But at present he wishes to show by empirical evidence, and independently of this axiom of endless divisibility, that there is more than one particular.

      McTaggart thinks that the occurrence of any sensation or introspection suffices to show that there are at least two particulars. Suppose it is the case that at a certain moment an event happens which would be described as a "hearing of a squeaky noise". There must then be something which is, or seems to be, a squeaky noise. Now anything that was, or seemed to be, a squeaky noise would quite certainly be a particular. But it is equally certain that the two statements: "There is something which is or appears to be a squeaky noise" and "There is a hearing of a squeaky noise" do not have the same meaning. We have seen that the latter could not be true unless the former were true, and many people would hold that the former could not be true unless the latter were so. Even if they do thus imply each other, their meaning is different; and I do not think that anyone would deny this when the question was fairly put to him, and all sources of possible confusion were removed. Now McTaggart maintains that what is described as "this hearing of a squeaky noise" either is a particular, and a different particular from that which is described as "the squeaky noise which is being heard", or, if not, involves a particular which is other than the latter.

      His own view is that the hearing of a squeaky noise is itself a particular, viz., an event which stands in a peculiar relation to the particular which is described as "the squeaky noise heard". If so, there are certainly two particulars, viz., this event and that other particular to which it stands in this peculiar relation. For he would regard it as obvious that the relation of sensation to sensum is one which no term could possibly have to itself. Other philosophers would propose other analyses of the situation. So far as I know, only two other analyses have been proposed. The first is that, whenever it is true to say that a squeaky noise is being heard the fact is that a certain self is standing in a certain direct relation, viz., that of sensing, to a squeaky noise. This analysis equally involves that there are two particulars, viz., this self and this noise. It is plain that there are two; for a noise cannot be a self, and a self cannot be a noise. The second analysis is as follows. Whenever it is true to say that a squeaky noise is being heard the fact is that a number of sensibilia and images are related at that moment in a characteristic way to each other and to that sensibile which is the squeaky noise in question. This again involves that there are other particulars beside the squeaky noise. And it does seem inconceivable that any satisfactory analysis of the situation could fail to involve this. So I agree with McTaggart that the occurrence of even one such situation as would be expressed by the statement "There is a hearing of a squeaky noise" would make it certain that there is more than one particular. And it is an indubitable empirical fact that situations which can properly be described by such a phrase do from time to time occur.

      McTaggart contends that we cannot use the occurrence of a judgment, as distinct from a sensation or an introspection, as a premise to prove that there is more than one particular. It is true that a judgment could not occur without there being awareness of at least two different terms. But the terms need not be particulars; they might be both universals. And some people would deny that the awarenesses of terms in a judgment are particulars. McTaggart himself holds that, whenever there is awareness of two terms, whether the latter be particulars or universals, there are two particulars, one of which is an awareness of one term and the other of which is an awareness of the other term. But he admits that many other philosophers would refuse to accept this view. They would hold that in such cases there is just one particular, viz., a certain self which is making the judgment, and that this stands in a certain direct relation, viz., that of being aware of, to the two terms. So, although for McTaggart himself the occurrence of any judgment involves that there are at least two particulars, even though the judgment should be wholly about universals, he could not expect everyone to accept the argument.

      On the other hand, McTaggart holds that the occurrence of knowledge that a judgment has occurred would prove to anyone that there is more than one particular, no matter what view he might hold about the nature of judgment. His reason for saying this is that knowledge that a judgment had occurred must rest on introspection of the judgment. The introspection of the judgment could then be treated on the same lines as the sensation of the squeaky noise, and the same conclusion could be reached as was reached in that case. This is not at all clear to me. Suppose a person thought that the occurrence of a certain judgment was the occurrence of a certain direct relation between a self and a number of terms, none of which is a particular. He might also think that the occurrence of an introspection of this judgment was the occurrence of a certain other direct relation between the same self and the complex whose terms are this self and these universals. There would not then be two particulars, but two different occurrences of a single particular, viz., of the self as judger and the self as introspector.

      In §75 McTaggart says that the fact that there is more than one particular could be established by such facts as that at certain times there occurs a sensation of a squeaky noise and a sensation of a red flash. It is certain that what is called "the squeaky noise" and what is called "the red flash" are different particulars. But, if we choose to be extremely sceptical, is it absolutely certain that they are different particulars? Is it inconceivable that one and the same particular should be sensed both as a red flash and as a squeaky noise?

      I should have thought that it would have been much safer to take the case of two co-existing sensations of the same kind, e.g., of a red flash and a blue one, or of two red flashes. It is certain that no particular could be both red and blue at the same time, or could be at two different places in the visual field at once. And it is almost inconceivable that a single particular could be sensed as red and as blue or be sensed as being at two different places in the visual field.

      In §77 McTaggart points out that the fact that there is a plurality of particulars is quite consistent with the fact that the aggregate of all particulars is a particular. On his definition, all collections of particulars are particulars. We shall return to this subject when we deal with his theory of Groups and Compound Particulars.