I have some questions about propositions of future like “tomorrow, there will be rain” or “you won’t go to school tomorrow”

1) Are there certain truth values of future propositions? For example, should we say there is no truth value of a proposition “there will be rain tomorrow” until it happens? If so, we would have to wait until the time that the proposition refers. Than it would have a truth value. But however, that seems odd to me.

2) What is the relationship between future-propositions and time theories? For instance, it seems in the B theory of time, the future-propositions' truth values would be certain etc.

3) What is the relationship between future-propositions' certainty and free will? If future-propositions’ truth values are certain at all time, doesn’t that mean there is no free will?

  • Such propositions are known as future contingents and SEP has long articles that addressing all these issues, see Future Contingents and Logical Fatalism. Could you focus your question more narrowly? Our policy is one question per question.
    – Conifold
    Commented Oct 25, 2017 at 19:07
  • 1
    I'd say that future contingents have no truth value. They are speculations.
    – user20253
    Commented Oct 26, 2017 at 9:20
  • For (3), even without free will we can have unpredictability. Quantum mechanics is stochastic, for example. Given a radioactive sample that emits an average of ten alpha particles per second, we can describe the probability of any given measurement in any given second, but we can't predict whether ten or more or nine or fewer alpha particles will be emitted. Commented Aug 14, 2018 at 20:36

4 Answers 4


Well semantically propositions have a definition that may be different in maths and science. So this means varying answers depending on which department did the teaching.

In philosophy I was taught all propositions have a truth value. You are now bringing up awareness of the truth value which sounds like a science approach. Because I don't know which value proposition x holds does not mean the proposition has no value. The proposition has a value but you are currently unaware of said value. To say the proposition has no value because you are unaware contradicts the standard definition that propositions must have a value of true or false and no other possibility. To conclude that propositions have no truth value because of ignorance does not seem well formed.

Free will expresses that one has alternatives available. Christians have free will because neither God or Satan can force them to behave in a certain way. That would be possession. As far as predestination goes--this comes up because of future propositions--technically it is all psychological. God knows the outcome but we don't. Our awareness would not be able to change the value even if we had it. If I am set to die 2 days before my next birthday, this is true independent of any human being. With or without your existence this proposition is true or false. What makes the proposition true is not human awareness. Today scientists claim to know that there is a super massive black hole at the center of each galaxy. Is one to believe this was not true in Aristotle's time because they were unaware?


I don't think that the person asking the question is confusing awareness of the truth value with existence of a truth value; I take the question to just be about the latter. As the question already suggests, under the B-theory of time it seems that the proposition in fact has a truth value (whether it is known or not). For the A-theory, that is less clear; some variants such as the moving spotlight theory seem to suggest that the proposition has a truth value, while for others such as presentism or the growing block theory this is less clear.

Sidestepping that, here's an argument that suggests it does have a truth value. Suppose I said yesterday "tomorrow it will rain" and then today in fact it does not rain. Today, people (correctly) judge that I was wrong. And this seems to go beyond saying that things happened to turn out in way that made me wrong. The judgment seems to be that even when it was still yesterday, I was already wrong. At least this would seem to be the commonsense interpretation, so if we want to say that there is a problem with this commonsense interpretation, we should have good reason to do so.


I am of the opinion that the principal of bivalence is overly simplistic and the B theory of time is nonsensical (of course, I'm currently throwing my lot in with the loop quantum gravity folks).

In reality, the truth value of the statement is in a superposition of both true and false. Or, if you'd rather think about it classically, the statment's truth value has a certain probability of being true or false.

  • I made an edit which you may roll back or continue editing. References would strengthen your answer and give the reader some place to go for more information. I would replace the loop quantum gravity with a reference to someone who takes a similar position that you do. Commented Aug 15, 2018 at 5:03

Take a step back. What hinges on the question of whether the bivalence principle (i.e. "every proposition must be either true or false") applies to propositions about future states of affairs? The rationale for presupposing the bivalence principle, in systems of logic, is that we wouldn't be able to prove much without it. We want to be able to make valid inferences about future states of affairs (similarly for propositions about fictional entities). So we should postulate that there are definite (not "certain," which implies knowledge of what the truth-value is, whereas "definite" just implies that the proposition has to be either true or false) truth-values for propositions about future states of affairs. It's just a convention of logic, not a reflection of any ontological truth. There is no right answer to whether propositions about future states of affairs have definite truth-values. Systems of logic can adjust themselves to different theories of time, or theories of free will, and vice versa. Philosophers bend their logic-theory to their time-theory or bend their time-theory to their logic-theory, depending on whether they're starting from theorizing about logic or starting from theorizing about time.

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