In the second chapter of Four Dimensionalism, Ted Sider offers a series of arguments against presentism. This paper will be an evaluation of one of these. I will argue that Sider’s truth-maker objection against presentism does not entirely succeed. Specifically, I will argue that the presentist can provide truth makers for claims about the past given present-to-past deterministic laws of nature.

Presentism is the view that past and future states of affairs do not exist. Of course, we make lots of claims about the past that we do want to count as true. The truth-maker objection to presentism is that presentism fails to recognize any existing entities in the world that could account for the truth of claims about the past or the future. Armstrong’s truth-maker principle holds that for every true proposition, there must be some existing entity that suffices for its truth. Sider prefers the formulation of the truth-maker principle offered by Lewis and Bigelow which requires only that truths superviene on existing entities. His reason for this preference is that it avoids problems in accounting for negative facts. There does not appear to be any entity, for instance, that suffices for the truth of "there are no unicorns". Though, it seems to me that the world at large suffices for the truth of negative facts. If so, I prefer Armstrong’s formulation of the truth-maker principle on the grounds that it does not saddle us with the need to explicate an appropriate notion of supervienience. But which of these formulations of the truth-maker principle one accepts will not be at issue in this discussion.

Past and future states of affairs, if we accept them, straightforwardly provide truth-makers for truths about the past and future. But the existence of such states of affairs is just what the presentist denies. So the presentist faces the daunting challenge of somehow getting presently existing entities to serve as truth-makers for truths about the past and future.

One avenue open to the presentist is to enlist laws of nature and take these in conjunction with presently existing states of affairs to provide truth-makers for facts about the past. Sider notes that a regularity theory of laws cannot serve the presentist’s purpose in accounting for past and future truths. Regularity theories take laws to be given in existing regularities. But according to presentism, the only existing regularities are those that hold at the moment. And whatever the presently holding regularities are, their holding presently is consistent with their failing to hold in the past or the future. So, a regularity theory of laws would leave the past and future entirely open and therefore fail to provide truth-makers for claims about the past we want to count as true.

Sider takes presentism’s incompatibility with the regularity theory of laws to count against presentism. However, I would not want to hold this commitment against presentism if the regularity theory of laws is false. In fact, I think there are compelling reasons for rejecting the regularity theory of laws which are independent of the presentism/eternalism issue. I will not canvas these here. But in addition to these, and in connection with the present point, it is worth mentioning that whatever weight the incompatibility of presentism and the regularity theory carries against presentism, it also carries against the regularity theory. For if presentism must appeal to laws to provide truth-makers for claims about the past, then the regularity theory of laws is equally burdened with a commitment to the falsity of presentism.

Sider discusses the realist view of laws offered independently by Armstrong, Tooley and Dretske as an account that is friendlier to presentism. According to that view, laws are second order nomic relations that hold between universals. Sider raises two objections to grounding truths about the past in truths about the present in conjunction with realist laws. The first is that if the laws are present-to-past indeterministic, this view would leave many facts about the past without a truth-maker. The presentist could accept that the past is open, that where the laws in conjunction with present facts fail to determine the past there simply is no fact of the matter as to what happened. Sider cites Jan Lukaseiwicz as one philosopher who is prepared to accept this result. But few will find this view acceptable.

But the indeterminism objection is not decisive. The presentist could be right if the laws are after all present–to-past deterministic. And the laws could be present-to-past deterministic even if they are not present-to-future deterministic. Causes that are not sufficient conditions for their effects may yet be necessary conditions. Sider’s second objection to grounding facts about the past in present states of affairs and the laws is that the past would remain open even if the laws are deterministic because facts about the present in conjunction with the laws fails to account for dynamic facts. Dynamic facts, facts about the velocities of bodies for instance, are required in order to account for truths about the past in terms of the present and deterministic laws.

We can get a more intuitive take on the problem by considering a time slice of a dynamic system. Consider then, the instantaneous state of a pool table and the balls on it a half second after the rack has been broken. The position of each of the balls is given in this state of affairs. But intuitively, there is nothing about the state of the balls on the table at that instant that determines the direction of travel and speed of the balls. Their velocity seems open. In order to ground facts about the past in facts about the present plus the laws of nature, the presentist must deny this and take velocity to be intrinsic to the present state of the balls on the table. Though we can identify several paths that are not open to the presentist, I think this can be done.

Velocity is a vector quantity that can be defined as speed or rate of motion with direction incorporated. Kinematics does employ a notion of "instantaneous velocity". But it will be of little help to the presentist since instantaneous velocity is defined in terms of the limit of rate of motion over successively shorter intervals of time.

The dominant theory of motion is given by Russell. According to Russell’s "at-at" theory of motion, "motion is the occupation, by one entity, of a continuous series of places at a continuous series of times." If velocity is to be analyzed in terms of motion, and if Russell gives the correct analysis of motion, then clearly the presentist is in trouble. I take it that an analysis is an account of the nature of a complex property in terms of its structure and simpler component properties. If velocity were to be analyzed in terms of Russell’s theory of motion, this would make velocity a complex relational property involving motion which in turn involves times other than the present. And such properties are not available to the presentist in providing truth-makers for claims about the past or future. But alternative accounts of velocity are available.

Michael Tooley offers an account of velocity that makes velocity intrinsic to the present. Tooley takes velocity to be a theoretical property and offers a theory "whose postulates will provide an implicit characterization of the concept of velocity." Tooley’s postulates include the following:

T1: s(x,t2) = s(x,t1) + t1∫t2 v(x,t)dt

In this formula the expression s(x,t) refers to the position of an object x at a time t, and the expression v(x,t) refers to the velocity of x at t. T1 chacterizes an object’s velocity as a theoretical property in terms of its nomic relations to the spatial locations of the object at different times. However, according to Sider, Tooley’s theory is not available to the presentist in providing truth-makers for claims about the past. Sider argues as follows:

On the view that laws are contingently holding nomic relations between universals, velocity has its nomic character in virtue of the nomic relations that hold between it and other universals. For the presentist, T1 must be understood as characterizing the nature of velocity in terms of its relations to tensed location properties. Velocity, on Tooley’s account, is intrinsic to the present. But given the realist theory of laws, positing velocity as a theoretical property intrinsic to the present requires accepting laws that nomically relate tensed properties. The presentist cannot legitimately invoke laws that involve tensed properties in providing truth-makers for tensed truths.

Given the realist theory of laws as contingent nomic relations between universals, Sider reaches the right conclusion. On this view of laws, the presentist can have dynamic properties intrinsic to the present only at the price of rendering dynamic laws unacceptable as presentist truth-makers for claims about the past. But the game is not over for the presentist. For, there is another account of laws that affords dynamic properties that are intrinsic to the present without grounding laws in tensed properties. On the realist theory of laws advanced by Tooley and Armstrong, universals stand in nomic relations contingently. On this view, the nomic character of a property depends on its nomic relations to other properties. But suppose we take properties to have their nomic character essentially. For instance, we might take properties to have their causal powers essentially. This view, know as dispositional essentialism, has a substantial and growing number of adherents. On this view, we can take T1 to characterize the essential nature of velocity as a theoretical property intrinsic to the present. Any description of the nomic character of velocity will still require reference to times other than the present. But what makes makes it a law that velocity has the nomic character described by principles like T1 is not the relation of velocity to other universals, but just the essential nature of velocity alone, and the essentialist presentist can take this property to be intrinsic to the present.

Let me explain the proposed move further in terms of dispositions generally and the properties that ground them. I take dispositions to be complex relational properties. Specifically, I take the disposition to M if P to be the property of having some distinct causal base property, a property which in conjunction with the precipitating condition P would constitute a causally sufficient condition for a manifestation M. Note that dispositions themselves are causally impotent. All of the causal work one might be tempted to ascribe to a disposition is done by the causal base property. It is the causal base property that has causal powers, not the relational disposition. We can only describe a property’s causal powers in terms of the dispositions it grounds. But it would be a mistake to conflate relational dispositions with the causal powers of properties. Dispositions are causally impotent, causal powers are not. Causal powers are intrinsic to their instances, dispositions are not.

This relational account of dispositions is compatible with the view of laws as contingent nomic relations defended by Armstrong and Tooley. Dispositional essentialism is the further view that causal base properties are dispositional in the distinct sense of having their causal powers essentially. On this view, laws indirectly characterize the nature of causal base properties by analyzing the dispositions they ground essentially. While laws will unavoidably make reference to the precipitating conditions and manifestations of complex relational dispositions, they are grounded in the distinct causal base properties that are intrinsic to their instances. It is a law that water expands when it freezes because being H2O is a causal base for water’s disposition to expand when it freezes. This law is grounded entirely in causal powers that are essential to being H2O. The property of expanding and the property of freezing are not required as truth-makers for its being a law that water expands when it freezes.

Were we to conflate relational dispositions with the causal powers of causal base properties, we could, albeit fallaciously, assert a stronger claim against the presentist than Sider does. We could charge that the presentist is denied dispositions as well as dynamical properties. This is because analyses of relational dispositions are temporally loaded in same way as T1. For a thing to have a disposition is for it to be such that given an occurrence of its precipitating conditions at a time, a manifestation would be produced at some later time. But neither charge against the presentist is warranted. We can only describe the causal powers of properties in terms of the dispositions they ground. But while the relational disposition is temporally loaded, its causal base is not. We can only represent the nature of velocity in terms of the temporally loaded principles it grounds. But as in the case of dispositions and their causal bases, the essentialist should deny that velocity is temporally loaded. And since it is velocity alone that grounds T1, the presentist can endorse T1 as characterizing velocity in terms of a complex relational property that is entailed by the essential nature of velocity

The essentialist accepts underlying theoretical properties like velocity or the causal bases of basic force dispositions as unanalyzable primitives. Their nature can be characterized in terms of the complex relational properties they ground. I take it that this is just what laws do. Elsewhere I have argued that causal laws are analyses of dispositions. What makes it true that a given analysis is a law is ultimately the essential natures of grounding properties that are themselves not subject to analysis. To speak metaphorically, we grasp the nature of the most fundamental properties of our world through the shadows they cast.

Laws represent the nomic characters of properties in terms of their relations to other properties. This much the contingent nomic relations realist and the essentialist can agree on. The essentialist takes properties to have their nomic character essentially. Laws describe connections to other properties that are necessitated by the essential nature of basic properties. Laws are not grounded in these connections to other properties, but in the essential nature of properties themselves.

By contrast, on the realist view championed by Armstrong Tooley and Dretske, a property’s nomic character is constituted by its connections to other properties and relations. Those nomic connections might have differed. Had the nomic relations a property stands in differed, then the nomic character of that very property would have differed. Yet there is nothing more to be said about the nature of a basic property than to describe its nomic character. Where we take properties to have their nomic character contingently, we are forced to accept "bare universals" or properties whose identity is primitive. And condoning bare universals has some counterintuitive consequences. Specifically, it opens up the possibility of what Brian Ellis calls a "global transubstantiation," an empirically indistinguishable world containing different kinds of things and processes. A global transubstantiation of the actual world would be a world that differed only with regard to what properties have what causal powers and instances. On Armstrong’s view, for instance, there is a possible way the world could be, a global transubstantiation, where the causal bases for electromagnetic dispositions and gravitational dispositions swap their causal powers and instances. This global transubstantiation would be empirically indistinguishable from the actual world. Indeed, intuitively, global transubstantiations are not really distinct possibilities. Yet a global transubstantiation is a distinct possibility on Armstrong’s view in virtue its nomic relations holding between different universals.

There are further reasons for preferring the essentialist position which I will not have time to offer here. But let us return to the pool table for a moment. Intuitively, it seemed that the state of the pool table at an instant did not determine the velocities of the balls. Theoretically, I think we’ve shown how the presentist can deny this. But the intuition lingers. I think this apparent intuition can and should be explained away. I don’t think we can imagine instantaneous states of dynamic systems any more than we can perceive them in isolation. When we try to imagine an instantaneous state of the pool table, what we in fact conjure up is an enduring static state. Of course in doing so, we strip away velocity. Our apparent intuition that the instantaneous state of the table lacks velocity is an artifact of the limits of human conceivability. But such identifiable limitations to conceivability should not constrain our metaphysics.

I find a methodological lesson for the metaphysician in this defense of presentism and in the broader essentialist program. It is that we should take care not to read our ontological views too directly off of our modes of representing the world; in this case, laws conceived of as representations of the nomic character of properties in terms of their connections to other properties. There is a significant risk of importing artifacts of our representational schemes into our ontology. And these artifacts are apt not to do justice to the underlying reality. Of course others may take this point not as a lesson, but as a contentious matter for meta-ontological debate. This is a debate I will be happy to join.

Works Cited

Ellis, Brian. Scientific Essentialism. Cambridge: Cambridge University Press, 2001.