Truth-Makers and Facts
As discussed in Chapter 1, according to truth-maker theory, truth-makers make propositions true or false. This allows an explanation of how' propositions can vary in their truth-values.
An important class of truth-makers is that of facts. Facts are specific kinds of entities, similar but not identical to events. They are not concrete particulars such as talking donkeys, but w'ays in which talking donkeys are. For example, in some possible, non-actual world, if talking donkeys are loud, then it is a fact that talking donkeys are loud.
Facts can be true or false, or the case or not the case; the terminology can vary. For example, it is the case or it is true that talking donkeys are loud; that is a fact. Furthermore, some facts are true in all possible worlds. For example, it is a fact in all possible worlds that the square root of 2 is irrational; there is no possible world in which the 2’s square root is rational.
Furthermore, some but not all facts are true in the actual world (and some are only true in the actual w'orld). For example, in the actual w'orld, it is a fact that the speed of light is finite. In some other possible world, light travels instantaneously, the speed of light is infinite, and it is not a fact that the speed of light is finite. (And, in the actual w'orld, it is not a fact that talking donkeys are loud, or anything else.)
Truth-Makers For Propositional Variation in Truth-Value
Some possible-world theories use truth-makers (including facts) to explain variations in proposition’s truth-values across different worlds.1 These typically involve concrete particulars2 with a specific relationship to propositions about them. Briefly,
• Each possible world has a different set of concrete particulars in it. Many of these particular fall under different types, types that are absent in other worlds.
For example, one possible w'orld W1 contains a set of particular talking donkeys; another w'orld W2 does not have such donkeys but has non-talking donkeys.
• These concrete particulars are truth-makers for certain propositions. That is, in the world containing them, they make certain propositions true; they can also make other propositions false.
For example, the proposition Pw donkeys can talk is true in IVI because IV1 has talking donkeys in it; the talking donkeys are truth-makers for Pw in Wl. However, in W2, Pw is not true, Pw is false, because there are no talking donkeys in W2 there are no talking donkeys to be truth-makers for Pw in W2.
Given this account, we can have a theory of propositions varying in truth- value over possible worlds. A proposition varies in truth-value across worlds if one world has the truth-maker and another world does not. Pw varies in truth- value from Wl to W3 because Wl has talking donkeys and W3 has not.
Perhaps we can apply similar reasoning to time. Each moment of time is an analogue of a possible world, leading to the following:
For example, the proposition PT there are dinosaurs is true at 77 because T1 has dinosaurs in it; the dinosaurs are truth-makers for PT in Tl. However, in T2, PT is not true, PT is false, because there are no dinosaurs in 72; there are no dinosaurs to be truth-makers for PT in 72.
In this way, we might say, propositions can change value by having different truth-makers at different times:
Similarly, we can explain the variation in truth-values of propositions about objects and their changing properties. For example, say that there is a proposition PRipi‘ that the apple is ripe. Then, similar to above, we have this situation.
If an apple is raw at one time (t,) and ripe at another time (t2), then:
риг? that the apple is ripe is false at t, (when the apple is raw) and true at t2 (when the apple is ripe).
From this account, it follows that different propositions are true or false at different times. For example, along with PRipe, there is PRaw, that the apple is raw.
pRaw js true at (when the apple is raw) and false at t, (when the apple is ripe).
However, there is an outstanding question here. It is the original question: how can propositions be true at a time?
Objection: Propositions Are Abstract and Not in Time
Lots of things have lots of properties in time. Donkeys talk loudly on a Tuesday. Similarly, it may be apparent that the proposition donkeys talk loudly is true on a Tuesday.
However, if propositions are abstract entities, then they are not in time. If propositions are not in time, then they cannot be anything at a time. If they cannot be anything at a time, they cannot be true or false at a time. If they cannot be true or false at a time, then they cannot vary their truth-value from one time to another.3