This double task cannot be settled by _a priori_ means but has to be approached by starting from empirical assumptions based on experience. If one has to acknowledge that the ways we are bound to conceive of all these experiential or phenomenal characteristics lead to contradictions then these characteristics cannot be true of reality. McTaggart’s strategy here is strongly reminiscent of Bradley’s procedure to downgrade many phenomena to appearances and to deny them the status of constitutive elements of reality. The empirically given characteristics McTaggart discusses primarily are (a) time, (b) matter, (c) sensa, (d) spirit and (e) cogitation. As to (a) time he denies that “anything existent [can] possess the characteristic of being in time” (_NE_ §303) where time is understood as an ordering relation between events. He distinguishes between two ways of ordering in time. The first gives rise to what he calls the “A-series” according to which every state of affairs (event, thing) is either past or present or future. The second, the so-called “B-series”, relates transitively and asymmetrically states of affairs in terms of earlier and later (cf. _NE_ §306). He claims that the A-series is more fundamental than the B-series because only the A-series can account for change (_NE_ §317) and goes on to demonstrate that (a) the A-series and the B-series contradict each other in the sense that they belong together though they are incompatible (cf. _NE_ §333) and that (b) the (more fundamental) A-series leads to time determinations of a state of affairs that are contradictory. The result: > We conclude that the distinctions of past, present and future are essential to time, and that, if the distinctions are never true of reality, then no reality is in time. (_NE_ §324) Though never true of reality these distinctions are not empty because according to McTaggart they have to be taken as appearances of a third series, the C-series, “a series which is not a time series, but under certain conditions appears to us to be one”. This C-series “does actually exist in every case in which there is the appearance of a time-series” (_NE_ §347). McTaggart thinks of the C-series (at least in _The Nature of Existence_) as an “Inclusion Series” (_NE_ §575) > whose members are connected by the relations “inclusive of” and “inclusive in”, so that of any two terms one will be inclusive of the other, and the other will be included in it. (_NE_ §575) Concerning (b) matter which he characterizes as “something which possesses the primary qualities” (_NE_ §355) he also wants to prove that it does not exist (_NE_ §364). This is so because all that exists are substances that have to be infinitely divisible. Matter, however, > cannot be divided into parts of parts to infinity either in respect of its spatial dimensions, or of that dimension which appears as temporal. And matter, as usually defines, and as we have defined it, has no other dimensions. … And therefore it cannot exist. (_NE_ §362) The existence of matter can also not be inferred on the basis of the prima facie existence of what I perceive “by means of the sense organs of our bodies”, i.e., of what he calls “sensa” (_NE_ §373), because it is erroneous to believe that matter as the presumed outside cause of a sensum has the same qualities as a sensum and thus has to exist (_NE_ §365). He conjectures that if there are outside causes of sensa they must be substances which are “of a spiritual nature” (_NE_ §371). When it comes to (c) sensa McTaggart holds that one has to distinguish between two classes of percepta, those perceived by introspection (mental states, spiritual data) and those that are given by means of sense organs (sensa). The latter do not really exist, they just lead to the illusion that they exist. This is so because of a confusion between a perception that is part of the percipient and therefore spiritual or mental in character and what is perceived, i.e., the object of a perception or the perceptum (_NE_ §373). However, a perceptum as a sensum cannot, according to McTaggart, have parts within parts to infinity and thus cannot really exist because what exists has no simple parts (cf. 355). Having disposed of matter and sensa this way, he then discusses the ontological status of (d) spirit or spirituality. He declares that “the quality of spirituality … is the quality of having content, all of which is the content of one or more selves” (_NE_ §381) and states that “nothing can have this quality except substances, and so nothing but substances are spiritual” and exist or are real (ibid.). A self or an I he takes to be a simple quality of a substance which is known to me to be myself by direct perception, i.e., is known by acquaintance, not by description. The distinction between knowledge by acquaintance and knowledge by description he explicitly takes up from Russell (_NE_ §382). He then surmises that it is very likely that the I, i.e., the substance that possesses the quality of being a self, persists through time because “I perceive myself as persisting through time, or the real series which appears as a time-series” (_NE_ §395). He also holds that selves are conscious without having to be self-conscious (_NE_ §397) and that no experience is possible “which is not part of a self” (_NE_ §400) though it cannot belong to more than one self (_NE_ §401). He concludes: > As all the content of spirit falls within some self, and none of it falls within more than one self, it follows that all existent selves form a set of parts of that whole which consists of all existent spirits. (_NE_ §404) Although written more than twenty years after G. E. Moore’s “The Refutation of Idealism” (see below) and without mentioning him at all, McTaggart thus arrives at the exact opposite to the conclusion that Moore defended. Regarding (e) cogitations which comprise perceptions, awarenesses of characteristics, judgments, assumptions, imaginings, only perceptions can form an infinite series required for existence (_NE_ §406). Perception he characterizes as awareness of a substance _as having_ such and such qualities (_NE_ §407). The outcome he wants to have reached so far is this: