The Atlas of Reality
Page 71
20.2 Varieties of Anti-Tensism
20.2.1 Reflexive thoughts and Old Anti-Tensism
One attempt to reduce tensed to untensed facts, what we'll call “Old” Anti-Tensism, makes use of reflexive thoughts. A reflexive thought is a thought that is partly about itself. Consider (11a), (11b), and (11r):
(11a) I ate breakfast three hours ago.
(11b) My eating of breakfast occurred at 9 a.m. on 5 July 2010.
(11r) My eating of breakfast occurred three hours earlier than the occurrence of this very thought.
(11a) is a tensed truth, and (11b) is a simple untensed truth. But (11r) is reflexive. (11a) and (11b) are clearly not equivalent: (11a) changes its truth-value from false to true and back to false, while (11b) remains true forever. Old Anti-Tensism proposes that (11a) is really equivalent to (11r), that (11a) is covertly a self-reflexive thought. However, (11a) is not even covertly about itself. It is not about thoughts or the times of their occurrence. Moreover, (11r) is an untensed truth. Its truth-value never changes. Hence, it cannot be logically equivalent to (11a). For these sorts of reasons, Old Anti-Tensism has been almost universally rejected.
20.2.2 Indexical propositions and New Anti-Tensism
New Anti-Tensism eliminates tensed propositions altogether and makes use of the theory of indexical sentences as a way of understanding the function of the tenses. An indexical sentence is one that contains an element, like ‘I’ or ‘here’, that indicates some fact about the context of use of a statement of the sentence. (The reader may want to remind themselves of Def 14.2, and of the discussion of Modal Indexicalism 14.2T.) The word ‘I’ picks out the speaker of the statement, ‘here’ the location of that speaker at the time of the utterance, and ‘now’ and present tense verbs pick out the time of the utterance. Similarly, the past tense picks out the range of times earlier than the utterance, and the future tense those times that are later. Compare (11a), (11b), and (11r) with (12a), (12b), and (12r):
(12a) I am warm.
(12b) RCK is warm.
(12r) The thinker of this very thought is warm.
The truth of (12a) (even when thought by RCK) is not a priori equivalent to the truth of (12b), nor to the truth of reflexive thought (12r). Nonetheless, it is plausible to think that whatever it is in the world that makes (12a) true, the truthmaker of (12a), when (12a) is entertained by RCK is the very same fact which makes (12b) true. Thus, whether we can reduce the truth of statements like (12a) to the truth of those like (12b) depends on what we are willing to count as a reduction.
In order to claim that the truth of (12a), when thought by RCK, reduces to that of (12b) or that the truth of (11a), when uttered on noon of the relevant day, reduces to that of (11b), we must embrace some version of Truthmaker Theory. Then, whenever something like (11a) or (12a) is true, the truth of these indexical statements is grounded in the truth of the propositions expressed fully and clearly by (11b) and (12b). That is, these truths are made true by non-indexical facts. This position has become more popular in light of the problems for Old Anti-Tensism noted above.
20.3 Varieties of Tensism
There are four ways of fleshing out the idea that being present is a property that times have temporarily. First, we could hypothesize that there is a simple, primitive, unanalyzable property of presentness that is possessed by one and only one moment at a time. This is often called “the Moving Spotlight Theory” because we can imagine the present as something like a spot of light that shines on a single moment and is constantly moving in the direction of the future. (This image was first employed by C.D. Broad 1923/1959.) The special “light” consists in the present moment's possessing some unique, irreducible quality of presentness.
20.2T.1 Simple Tensism (Moving Spotlight Theory). There is a simple, primitive property of presentness that is uniquely and temporarily possessed by a moment of time.
We have to add that this same property has been possessed by past moments and will be possessed by future ones. If we could analyze tensed propositions into tenseless ones, this claim would collapse into the triviality that each moment is (tenselessly) present when it is present. Thus, Simple Tensers have to embrace Tensism, refusing to reduce tensed propositions to tenseless ones.
Second, we have Falling Branches Tensism, proposed by Storrs McCall (1976, 1994).
20.2T.2 Falling Branches (Changing Possibility) Tensism. The present moment is the earliest moment such that all later times involve at least one contingent fact.
Falling Branches Tensism has a critical focus on a particular feature of modality, namely, the changing status of possibility or contingency. The future is characterized by contingency. Every future moment is such that there are some still contingent propositions concerning that moment, and these future contingent propositions represent alternative possible scenarios. The present and past, in contrast, are closed and fixed. The present moment is the latest of the closed moments and the earliest of the moments that are succeeded entirely by open moments. In other words, the present moment is the earliest branch point. As time progresses, possible branches, which represent alternative scenarios, “fall off” the tree of time. They cease to be possible once their moment of potential actualization has passed.
Third, there is another variety of Modal Tensism, Tensism that appeals to a modal notion. Aristotelian or Changing Actuality Tensism is the claim that there is one moment that is uniquely actual or real:
20.2T.3 Aristotelian (Changing Actuality) Tensism. The present moment is uniquely actual.
Changing Actuality Tensism itself comes in a variety of forms, depending upon the account of actuality that we embrace (see Chapters 14 and 15). If, for example, we adopt Existence-Simpliciter-Defined Anti-Indexicalism (15.2T.5), then Aristotelian Tensism is equivalent to Presentism, the fourth form of Tensism, introduced below.
The most interesting version of Aristotelian Tensism is one that builds upon Hybrid Anti-Actualism:
Hybrid Anti-Actualism Some things don't exist, but all concrete states of affairs (or all nexuses between properties and substances or all bundles of properties) exist.
On the combination of Aristotelian Tensism and Hybrid Anti-Actualism, all concrete states of affairs (nexuses, bundles) exist actually, and so all states of affairs (nexuses, bundles) exist in the present moment. This is because, according to Aristotelian Tensism, only the present moment is actual. However, there are many things, such as ordinary particulars, events, tropes, or bare particulars, that do not actually exist and that can therefore be located entirely in the past or future. These merely-past or merely-future things can be parts of the truthmakers for past-tensed and future-tensed truths.
Fourth, there is Existential Tensism, usually called ‘Presentism’.
20.2T.4 Presentism (Existential Tensism). The present moment is the unique moment such that everything exists then. That is, absolutely everything exists in the present moment and only then.
According to Presentism, the uniqueness of the present moment consists in the fact that everything exists in the present: that is, nothing exists wholly in the past or the future.
Before we consider Presentism more thoroughly, it is worth contrasting it with the view of what exists that is most naturally combined with Anti-Tensism, namely Eternalism:
20.2A.2T Eternalism. Everything that exists in the past, present, or future exists simpliciter.
Eternalism is the claim that past, present, and future moments are all metaphysically on a par, at least with respect to existence. The past and future exist no less than the present does. We can gain clarity about Eternalism by considering the indexical Anti-Tenser strategy discussed above. On that view, it is very natural to think that the present moment is much like one's present location in space: it's just one among many moments of time, and not metaphysically special in any deep way. To say that something is “here” is simply to locate it where you are. Likewise, it's natural for Anti-Tensers to think that to say that something exists “now” is simply
to locate it at a particular moment of time. That something isn't here is no bar against its existence. Likewise, that something is past or future is no bar against its existence. Dinosaurs and Martian colonies may not exist now, but they nonetheless exist. Simple Tensism is also helpful in understanding Eternalism: the spotlight moves along the four-dimensional, Eternalist universe.
(Strictly speaking, Anti-Tensism does not entail Eternalism. However, non-Eternalist Anti-Tensism is, for the reasons outlined here, a strange hybrid. In what follows, we treat Anti-Tensers as committed to Eternalism.)
20.4 Presentism
We have to distinguish Presentism from the following triviality: everything that exists in the present exists in the present. (13) is obviously trivial:
(13) Everything that exists in the present exists then.
(13) simply says that the present moment is the present moment. Everyone, even Anti-Tensers, agree with that. The simplest way to distinguish Presentism from the triviality of (13) is to adopt Actualism (12.1T), the thesis that everything exists. Anti-Actualists (12.1A), whether Possibilist (12.1A.1T) or Meinongian (12.1A.1A), cannot be Presentists (in the sense we have articulated), since they insist that some things do not exist at all, whether in the past, present, or future. Anti-Actualists would need to be Possibilistic Presentists:
20.2T.4.1 Possibilistic Presentism. The present moment is the unique moment at which everything that actually exists (simpliciter) actually exists then.
There is one further issue of interpretation with respect to these two varieties of Presentism: how are we to understand the verb ‘exists’? Obviously, we cannot understand it as a simple, present-tense use of ‘exists’, or else we would again produce the trivial (13) or its Possibilist counterpart (14), which is no less trivial:
(14) Everything that actually exists in the present actually exists then.
So to make sense of Presentism, we must understand the verb ‘exists’ tenselessly. Consider, for example, (15) and (16):
(15) Two plus two is four.
(16) The date of the beginning of the Civil War is earlier than the date of the beginning of World War I.
It's plausible to think that the verb ‘is’ in (15) and (16) is tenseless. Two plus two didn't become four at some point in time nor could they ever cease to add up to four. Similarly, 1865 is eternally earlier than 1914. Such facts couldn't possibly change with the flow of time.
Nonetheless, some Tensers (like Arthur Prior 1957, 1967, 1968 and Richard Gale 1968) have denied that there is such a thing as tenseless verbs. These are Serious Tensers:
20.2T.5 Serious Tensism. Only tensed truths are metaphysically fundamental.
For Serious Tensers, the right way to understand the verb ‘is’ in (15) and (16) is as an abbreviation for the conjunction ‘always was, is, and always will be’. The past, present, and future tenses are fundamental and cannot be eliminated from a perspicuous statement of the facts.
For Presentists who are Serious Tensers, the verb ‘exists’ as it occurs in the statement of Presentism or Possibilistic Presentism is either a present-tense version of ‘exists’ or the disjunction ‘has existed, exists, or will exist’. The first interpretation results in the trivial (17) and the second in the apparently absurd (18).
(17) Everything that exists in the present exists in the present.
(18) Everything that has existed, exists, or will exist exists in the present.
Actualists who are Presentists can, however, embrace (18), since they insist that absolutely everything exists. Consequently, Actualistic Presentists can (surprisingly) affirm (19) and (20):
(19) Everything that has existed still exists.
(20) Everything that will exist exists already.
Actualistic Presentists deny that some dinosaurs once existed. And they hold that absolutely nothing was once a dinosaur. But they can affirm that there once were some dinosaurs. In other words, Actualistic Presentists accept (21) and deny (22):
(21) In the past: (There exists an x: x is a dinosaur).
(22) There exists an x: (In the past: x is a dinosaur).
Since the existential quantifier (‘There exists an x’) occurs only within the scope of the past-tense operator (‘in the past’) in (21), Actualistic Presentists can assert (21) without accepting that there exist any dinosaurs. The quantifier cannot be exported from within the past-tense operator. Consequently, for Actualistic Presentists, it is a trivial truth that everything that exists in the past, present, or future exists in the present, since there is nothing that exists merely in the past or merely in the future. For Actualistic Presentists to assert (18), (19), or (20) is no more shocking than for them to assert something like (23) or (23*):
(23) Everything that exists in actuality or is a unicorn exists in actuality.
(23*) Everything that exists in the present or is a dinosaur or a Martian colony exists in the present.
For Actualists, (23) is trivially or vacuously true, since there are no unicorns. For Actualistic Presentists, (23*) is also vacuously true, since there aren't any dinosaurs or Martian colonies. In modern logic (that is, since Frege), any statement of the form ‘All A's are B's’ is vacuously true whenever there are no A's, since to say that all A's are B's is simply to say that no A is not a B. If there are no A's, then it's impossible for any A to fail to be a B. In such cases, logicians say that the statement ‘All A's are B's’ is vacuously true.
Def D20.2 Vacuous Generalization. A generalization of the form ‘All A's are B's’ is vacuously true if and only if there are no A's.
Therefore, for Actualists, (24) is vacuously true:
(24) Every unicorn exists in actuality (that is, there are no unicorns that do not exist in actuality).
There are no unicorns that do not exist in actuality because there simply are no unicorns period. For the same reason, it is true that all unicorns are three-legged or ugly or have round square horns. These are all vacuously true for Actualists, since there are no unicorns at all.
In contrast, Possibilists and Meinongians reject (23) and (24). For similar reasons, they must reject (18), since, for them (18) would entail that dinosaurs still exist and Martian colonies exist already.
We will assume, then, that Presentists who are Serious Tensers are also Actualists. In contrast, Simple Tensers and Modal Tensers, whether Falling Branches or Aristotelian, in contrast, could be Possibilists or even Meinongians. So, too, could Presentists who are not Serious Tensers, since such Presentists can insist that (14) be interpreted as using a tenseless ‘to be’ in the subject term:
(14*) Everything that actually exists (tenselessly) actually exists in the present.
There is a variation on Presentism that has been proposed by C.D. Broad (1923) and others: Growing Block Tensism. On this variation, we are to suppose that the present is the latest moment at which anything that exists exists. That is, the Growing Block Tensists suppose that everything exists either in the past or the present. Nothing exists solely in the future. The present moment is, therefore, the “leading edge of reality”. The future is wholly unreal, but once something becomes real, it stays real forever after.
One last point about Presentists. It is important to recognize the difference between Presentists and Solipsists of the Present Moment. Both agree that only the present moment exists. However, Solipsists also deny that there ever were or ever will be any other moments. In fact, they deny all tensed propositions: nothing was or will be. In contrast, Presentists are Tensers. They not only affirm past-tensed and future-tensed propositions; they also believe that some of these are among the world's fundamental truths.
THE PRESENTISTS' SOLUTION TO THE PARADOX OF INTRINSIC CHANGE Put simply, the paradox on intrinsic change consists in the problem of accounting for how it is possible that one and the same entity should have one intrinsic property at one time and a contrary property at another time. For example, how could one and the same bit of clay go from being hot to being cold, or from being cubical to being spherical. L
eibniz's Law tells us that if a thing A is identical to a thing B, then A and B must have all the same properties. If the clay goes from exemplifying the property of being hot to exemplifying the property of being cold, then the clay before the change, C1, exemplifies a property that the clay after the change, C2, does not. Therefore, C1 cannot be identical to C2. This is paradoxical because it is intuitively plausible for things to change properties (see Chapters 24 and 25 for more on this and related problems).
Presentists have the option of taking tense seriously. They can claim that the clay must now be either cubical or not cubical, hot or not hot. However, it is possible for it to be hot now but to have been cold (in the past), or to be going to be cold (in the future). The contradiction between being hot (now) and not hot (then) is dissolved, since the latter assertions occur with a past or future tense. As linguists and logicians put it, these uses occur “within the scope of a tense operator”. We can put the assertions in these forms:
(25) Clay is hot.
(26) WAS(Clay is not hot).
(27) WILL(Clay is not hot).
There is no need for a present-tense operator. To say that something is (present-tense) hot is simply to ascribe the property of being hot to it, without qualification.
Tense operators are non-factive. From WAS(p) or WILL(p), nothing follows about the present. In particular, from WAS(There exists an F), nothing follows about the existence of F's simpliciter. So, a commitment to (26) and (27) does not commit Presentists to there being something identical to the clay that lacks the property of being hot.